hi Jean,
thanks for the info. my advice given the above would be to look into the Running Total Expert (rt) as opposed to using a Summary. with the rt you can set when an addition is evaluated and when it is reset.
please have a look at the attached report file as an example. extract the contents and change the .txt extension to .rpt.
to create a Running Total using the rte just right click on the field that you use to make the summary file.
cheers,
jamie