Reports :: Grouping With Information From Multivalue Fields

I have a table which now contains a couple of hundred records with more than thirty fields each, and will ultimately contain over 1000 records. Some of these fields use the multiple value feature, and the fields and the forms which fill them work beautifully. Now comes the challenge.

Without going into detail that I'm not at liberty to share, I can say that there are different offices which have different people who are responsible in different ways for the work covered in these records. It is possible for each record to have multiple people assigned to it from the same office. This requires setting the control that shows the people from each office to allow multiple values. I need to be able to create a report which will allow me to hand a list of all the records each person is responsible for in the office to the person responsible, in spite of the fact that this will mean records will show up on more than one person's report.

Before I knew that there might be multiple people in the office for each record, I created great reports grouping and ordering by this office's control and field. Now, since they allow and store multiple values, I can't use them any more. I need to be able, as I said above, to get the same effect. I think the answer lies in some sort of calculated field or formula that applies text filters. What I need to be able to do is look in the field for this office and see if a person's name is contained in the field for that particular record, regardless of who else might be in the field, too. I need to be able to use the results from this filter or calculation or formula to generate something I can use in the group and order by processes.