multi-select fields and report builder

multi-select fields and report builder

Hello,
Is there a work around (via deluge script or else) to allow data in multi-select fields be grouped or filtered  in the report builder?  We have activities that are participated by multiple participants  that we input via look up -multi-select fields.  We need to make a monthly report for each of the participant vis-a-vis the collective activities they have participated. How can we do this here?

Its a  feature we commonly used at dabbledb.

Thanks,

Edith