Macro is being driven on different worksheets

[SamT]

ThisWorkbook

Private Sub Workbook_SheetActivate(ByVal Sh As Object)
If Sh.Name = "My Sheet" Then shwMsg
End Sub

Private Sub Workbook_SheetDeactivate(ByVal Sh As Object)
If Sh.Name = "My Sheet" Then
'Cancel Application OnTime
end if
End Sub