View this Google "filemaker time calculations"
There is something here - I am just unwilling to search further.
I think it was a Dwayne Blog entry or multiple entrys.
Couldn't it be something like:
Case (starttime <= filterStartTime and endTime >= filterEndTime ; filterEndTime - filterStartTime ;
endTime > filterEndtime and starttime >= filterStartTime and starttime < filterendtime ; filterendTime - starttime;
starttime <= filterStarttime and endtime < filterEndTime and endtime > filterStarttime ; starttime - filterstarttime)
Thanks for your thoughts gentlemen. Someone was able to give me this simple but effective calculation over on fmforums, I provide it here for the record:
Max ( Min ( RangeEnd ; EndTime ) - Max ( RangeStart ; StartTime ) ; 0 )