The easiest way that I can think of is to name the textboxes with a fairly
simple name like "Page1Box1".  Then you can write a sub that looks for a
specific pages text box, extract a number value from it, add 1 to it, and
change text in a target text box.

So to Name the text boxes (if you don't want to write a sub to do it),
select the first page textbox, and go to the immediate window on the Visual
Basic Editor.  Type:

ActiveDocument.Selection.ShapeRange.Shape.Name = "BoxName"

where "BoxName" Name is the name of your textbox.  Keep in mind that all
names must be unique.  You cannot have two shapes of the same name on a page,
and if there are two shapes of the same name in a document, only first one
encountered by the program will be returned when referring to them.

Next, create a sub similar to the one below (This assumes that the text
boxes being changed have "Page" and a number in them like "Page 1":

Public Sub TextBoxChanger()
Dim Page1box as Shape
Dim TempString as String
Dim TempByte as Byte
Set Page1box = ActiveDocument.Pages(1).Shapes("Page1Box")
TempString = Page1box.TextFrame.TextRange.Text
'Extracts the number whether 1 or 2 digits from the end of the string
TempByte = Right(TempString, Len(TempString) - InStr _(1,TempString, "
",vbBinaryCompare)

'Loop the following to do multiple pages or leave it as is to just take care
of the next page.
TempByte = TempByte + 1
ActiveDocument.Pages(2).Shapes("Page2Box").TextRange.TextFrame.Text = "Page
" & TempByte

Cory