Luc,
Building reports at runtime can be pretty powerful. I use a base report, copy it to another .frx file adding records and then tell it to run the generated report. You should just create a report and go poking around in the .frx file with the browser. The units of measurement are 10,000ths of an inch.
Look for the GenRepoX utility it does a lot of stuff along these lines.
>Does anybody, know how to create a .frx file at runtime.
>
>I do have the .frx structure, but don't know all the impact.