I believe you will need two pages if you want to get double-sided out of the printer. You could send 50 copies of a two page document as a more elegant way of getting 100 impressions.
Also, I would use content controls to hold the page x of y information as the coding will be far simpler. Aircode of the concept might be along these lines
Code:
lngNum = Val(InputBox(msgPgNum, ttlPgNum, strDefault))
For lngCur = 1 to lngNum Step 2
ActiveDocument.ContentControls(1).Range.Text = lngCur & " of " & lngNum
ActiveDocument.ContentControls(2).Range.Text = lngCur + 1 & " of " & lngNum
Next lngCur