Cancel a report from a form

Hi,
I have a report that calls a form in a loop.
The form is for writing the content of report lines.
That works fine.... But now I want a cancel button on that form,
that should cancel the form and the report.
If I set variable that I check for cancel the loop the report ignores it
and runs the loop til the end.
How can I cancel the loop or how can I close the report after
setting the variable with the cancel button?

Does anyone have an idea?

Regards,
Red