Filter required for multigroup fields to be at the same delta

I have to handle teams. The data structure is: Name, Team, Function
Some people have more than one function or are in more than one team. This I handle via a multigroup with Team and Function as fields.
Lets assume Fred is player in team-a and trainer in team-b.
Filtering for "team = team-a" and "function = trainer" gets Fred selected but he is not a trainer in team-a.
This could be solved by a filter which requires, that the delta-value for the 2 fields (Team and Function) are the same. The delta-values are available in the filter section, but there is no option, to request them to be equal. I think such filtering would be required.
Best regards
Werner