Add Footer In All Workbooks

I want a footer to appear on every Excel workbook that I open. Including the following code in ThisWorkbook of each workbook works, but I want it to work on any workbook, i.e. by including the code in ThisWorkbook of my Personal Workbook (personal.xls)

Private Sub Workbook_Open()
Dim ws As Worksheet
Application. ScreenUpdating = False
For Each ws In ActiveWorkbook.Worksheets
Application.StatusBar = "Changing footer in " & ws. Name
With ws.PageSetup
.LeftFooter = "&7Page &P of &N" & Chr(13) _
& "Path : " & ActiveWorkbook.FullName & Chr(13) _
& "Printed on &D at &T"
End With
Next ws
Set ws = Nothing
Application.StatusBar = False
End Sub

However, when I include the code in Personal.xls, I receive the following error message when I open an Excel file: Run-time Error '91': Object variable or With block not set