If you don't need to do it with code, it is easy. There is an AutoText entry
on the menu on the Header/footer toolbar to do it.

The method you are using will cause editing problems. In my documents it
inserts a frame with margins such that the page number can't even be seen.

Otherwise, you insert a page field and a numpages field in the header or
footer where you want it.

The following works if normal.dot is the attached template (and has its
native AutoText).

Sub InsertPageXofY()
'
' Macro written 10/14/2005 by Charles Kyle Kenyon
'
   Dim rFooter As Range
   Set rFooter =
ActiveDocument.Sections(1).Footers(wdHeaderFooterPrimary).Range
   ActiveDocument.AttachedTemplate.AutoTextEntries("Page X of Y").Insert _
       Where:=rFooter, RichText:=True
End Sub

I create templates that have the headers/footers and other structures I want
and simply create documents based on them. It is a lot simpler than using
code. http://addbalance.com/usersguide/templates.htm

BTW the term is Page X of Y, at least around here.