这就是你想要的吗？

Sub Select_last_rowrange_selection()
    Dim lastrow As Long
    lastrow = Range("b1").Worksheet.UsedRange.Rows.Count
    
    'this will select the column B used range
    Range("b2:b" & lastrow).Select
    
    'this will select the last row of column B
    Range("b" & lastrow).Select
End Sub

Sub Select_last_row_from_range_selection()
    Dim lastrow As Long, rng As Range
    Set rng = Selection
    lastrow = rng.Rows.Count
    'this will select the last row of selected range
    rng.Rows(lastrow).Select
End Sub

Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
    rem select only one cell
    If Target.Cells.Count = 1 Then
'        ...
    rem select more than one cells
    Else
'        ...
    End If
End Sub