VBA Help needed Fast

(How do you get the user to select cell A1?) IF he/she does not select A1, there should be a msgbox appearing to tell them to select A1. What is the vba code for this?

Workbook_SheetSelectionChange

Private Sub Workbook_SheetSelectionChange(ByVal Sh As Object, ByVal Target As Range)
If Target.Address <> "$A$1" Then
MsgBox "Please select cell A1"
End If

End Sub