formula to compare value among detail lines in different subreports

[RHRII]

The report I'm working with has two subreports. Both subreports have details listed. I need to be able to compare a value in each of the detail lines in one subreport to a value in each of the detail lines in the other subreport. For example, find the detail line in subreport A that has a date that matches a date in a detail line in subreport B. Any advice would be greatly appreciated!

Thanks,

Robert