我得到了罗布·博维的《专业Excel开发》一书，它让我大开眼界。
我正在用错误处理重新编写代码。但是，有很多我不明白。我特别需要知道如何在函数中正确使用它。我使用Bovey的错误处理程序的rethrow版本（在底部）。当我开始的时候，我使用的是基本的boolean（非rethrow）方法，并将我的子例程转换为boolean函数。（P.S.我将根据答案切换回布尔方法。
我需要关于如何将函数放入此方案的指导。我希望它们返回它们的真实的值（例如，一个字符串或双精度型，或者在某些情况下失败时返回-1），这样我就可以将它们嵌套在其他函数中，而不仅仅是返回一个错误处理布尔值。
这就是在入口点中对bDrawCellBorders(myWS)的典型子例程调用的样子。子呼叫似乎工作得很好。（也就是说，它是一个子例程，只是被转换成一个函数，以便它可以返回一个布尔值到错误处理方案。

Sub UpdateMe()  ' Entry Point

    Const sSOURCE As String = "UpdateMe()"

    On Error GoTo ErrorHandler

    Set myWS = ActiveCell.Worksheet
    Set myRange = ActiveCell
    myWS.Unprotect

' lots of code

    If Not bDrawCellBorders(myWS) Then ERR.Raise glHANDLED_ERROR    ' Call subroutine

' lots of code

ErrorExit:
    On Error Resume Next
    Application.EnableEvents = True
    myWS.Protect AllowFormattingColumns:=True
    Exit Sub

ErrorHandler:
    If bCentralErrorHandler(msMODULE, sSOURCE,,True) Then  ' Call as Entry Point
        Stop
        Resume
    Else
        Resume ErrorExit
    End If
End Sub

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但是，我不知道如何将其扩展到真实的的函数。这是基于书中的一个例子，这个例子是为一个子例程起草的，我只是把它切换到一个函数。
问题：

• 我该怎么称呼它？是否简单地像x = sngDoSomeMath(17)
• 它的错误处理功能是否正常？
• 使用bReThrow=true调用错误处理例程的正确位置在哪里？

代码：

Public Function sngDoSomeMath(ByVal iNum As Integer) As Single
    
Dim sngResult As Single

Const sSOURCE As String = "sngDoSomeMath()"

On Error GoTo ErrorHandler

' example 1, input did not pass validation. don't want to 
' go up the error stack but just inform the
' calling program that they didn't get a good result from this 
' function call so they can do something else
If iNum <> 42 Then
    sngResult = -1    'function failed because I only like the number 42
    GoTo ExitHere
End If

' example 2, true error generated
sngResult = iNum / 0

sngDoSomeMath = lResult

ExitHere:
    Exit Function
ErrorHandler:

' Run cleanup code
'  ... here if any

' Then do error handling

If bCentralErrorHandler(msMODULE, sSOURCE, , , True) Then ' The true is for RETHROW
    Stop
    Resume
End If

End Function

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错误处理程序例程：

'
' Description:  This module contains the central error
'               handler and related constant declarations.
'
' Authors:      Rob Bovey, www.appspro.com
'               Stephen Bullen, www.oaltd.co.uk
'
' Chapter Change Overview
' Ch#   Comment
' --------------------------------------------------------------
' 15    Initial version
'
Option Explicit
Option Private Module

' **************************************************************
' Global Constant Declarations Follow
' **************************************************************
Public Const gbDEBUG_MODE As Boolean = False    ' True enables debug mode, False disables it.
Public Const glHANDLED_ERROR As Long = 9999     ' Run-time error number for our custom errors.
Public Const glUSER_CANCEL As Long = 18         ' The error number generated when the user cancels program execution.

' **************************************************************
' Module Constant Declarations Follow
' **************************************************************
Private Const msSILENT_ERROR As String = "UserCancel"   ' Used by the central error handler to bail out silently on user cancel.
Private Const msFILE_ERROR_LOG As String = "Error.log"  ' The name of the file where error messages will be logged to.

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Comments: This is the central error handling procedure for the
'           program. It logs and displays any run-time errors
'           that occur during program execution.
'
' Arguments:    sModule         The module in which the error occured.
'               sProc           The procedure in which the error occured.
'               sFile           (Optional) For multiple-workbook
'                               projects this is the name of the
'                               workbook in which the error occured.
'               bEntryPoint     (Optional) True if this call is
'                               being made from an entry point
'                               procedure. If so, an error message
'                               will be displayed to the user.
'
' Returns:      Boolean         True if the program is in debug
'                               mode, False if it is not.
'
' Date          Developer       Chap    Action
' --------------------------------------------------------------
' 03/30/08      Rob Bovey       Ch15    Initial version
'
Public Function bCentralErrorHandler( _
       ByVal sModule As String, _
       ByVal sProc As String, _
       Optional ByVal sFile As String, _
       Optional ByVal bEntryPoint As Boolean, _
       Optional ByVal bReThrow As Boolean = True) As Boolean

    Static sErrMsg As String

    Dim iFile As Integer
    Dim lErrNum As Long
    Dim sFullSource As String
    Dim sPath As String
    Dim sLogText As String

    ' Grab the error info before it's cleared by
    ' On Error Resume Next below.
    lErrNum = ERR.Number
    ' If this is a user cancel, set the silent error flag
    ' message. This will cause the error to be ignored.
    If lErrNum = glUSER_CANCEL Then sErrMsg = msSILENT_ERROR
    ' If this is the originating error, the static error
    ' message variable will be empty. In that case, store
    ' the originating error message in the static variable.
    If Len(sErrMsg) = 0 Then sErrMsg = ERR.Description

    ' We cannot allow errors in the central error handler.
    On Error Resume Next

    ' Load the default filename if required.
    If Len(sFile) = 0 Then sFile = ThisWorkbook.Name

    ' Get the application directory.
    sPath = ThisWorkbook.Path
    If Right$(sPath, 1) <> "\" Then sPath = sPath & "\"

    ' Construct the fully-qualified error source name.
    sFullSource = "[" & sFile & "]" & sModule & "." & sProc

    ' Create the error text to be logged.
    sLogText = "  " & sFullSource & ", Error " & _
               CStr(lErrNum) & ": " & sErrMsg

    ' Open the log file, write out the error information and
    ' close the log file.
    iFile = FreeFile()
    Open sPath & msFILE_ERROR_LOG For Append As #iFile
    Print #iFile, Format$(Now(), "mm/dd/yy hh:mm:ss"); sLogText
    If bEntryPoint Or Not bReThrow Then Print #iFile,
    Close #iFile

    ' Do not display or debug silent errors.
    If sErrMsg <> msSILENT_ERROR Then

        ' Show the error message when we reach the entry point
        ' procedure or immediately if we are in debug mode.
        If bEntryPoint Or gbDEBUG_MODE Then
            Application.ScreenUpdating = True
            MsgBox sErrMsg, vbCritical, gsAPP_NAME
            ' Clear the static error message variable once
            ' we've reached the entry point so that we're ready
            ' to handle the next error.
            sErrMsg = vbNullString
        End If

        ' The return vale is the debug mode status.
        bCentralErrorHandler = gbDEBUG_MODE

    Else
        ' If this is a silent error, clear the static error
        ' message variable when we reach the entry point.
        If bEntryPoint Then sErrMsg = vbNullString
        bCentralErrorHandler = False
    End If

    'If we're using re-throw error handling,
    'this is not the entry point and we're not debugging,
    're-raise the error, to be caught in the next procedure
    'up the call stack.
    'Procedures that handle their own errors can call the
    'central error handler with bReThrow = False to log the
    'error, but not re-raise it.
    If bReThrow Then
        If Not bEntryPoint And Not gbDEBUG_MODE Then
            On Error GoTo 0
            ERR.Raise lErrNum, sFullSource, sErrMsg
        End If
    Else
        'Error is being logged and handled,
        'so clear the static error message variable
        sErrMsg = vbNullString
    End If

End Function

型