PageBreak after x items for group, different on first page

I am trying to add a page break for table details after x items with x being different for the first page of report.

I am able to add a page break by adding a group to table with group expression =Int((RowNumber(Nothing)-1)/25). But I can't figure out how to do this where groupexpression on page 1 of report = Int((RowNumber(Nothing)-1)/15) and on all other pages =Int((RowNumber(Nothing)-1)/25).

I tried

=IIF(Globals!PageNumber=1,Int((RowNumber(Nothing)-1)/15),Int((RowNumber(Nothing)-1)/25))

but Globals cannot be used in group expression. I also tried putting group expression in a textbox on the report but it will not let me refer to the textbox.

Any assistance is appreciated!
Chris

references: http://msdn2.microsoft.com/en-us/library/ms157328.aspx , http://msdn2.microsoft.com/en-us/library/ms157328(en-US,SQL.90).aspx

Try a group expression like this:

=iif(RowNumber(Nothing) <= 15, Int((RowNumber(Nothing)-1)/15), Int((RowNumber(Nothing)-1-15)/25))

This should result in 15 rows for the first page, and 25 rows on subsequent pages.

-- Robert