About rpt function

I am creating an invoice using data reports.It contains four sections.I want the total of invoice should come in page footer.For first page it should display sum of first dislayed records then in next pages it should display sum of first page and the item amount of next pages.

if i use a label in page footer then the problem is how to retrieve value from rpt function.

if i display the sum in group footer it displays the sum just after the records finished .

any expert in data report ....

You can create a ... a..... oh, man I forget the name of it..... not a formula.....

Running Total Field.... that's it..... you can tell it what field to sum up, and how often to reset it's self.

When I add a header/footer to my datareport, add a report function field bound to one of the fields in my dataset and run the report, I get an error that says:

"report sections do not match datasourse"

What am I doing wrong?????