You don't need a group to use distinctcount. Create a formula:
whileprintingrecords;
shared numbervar uniqID := distinctcount({table.ReqID});
Place this in the subreport footer. Then in the second subreport, use a formula like this to reference the number:
whileprintingrecords;
shared numbervar uniqID;
You have to use shared, not global, variables if you want data to be shared between subreports or between main and subreport.
Where are your subreports located? If the subreports are placed in group sections and are linked to the main report on the group field, then the shared variable results will be per group (without changing the formula above).
Note that to pass successfully, the second subeport needs to be in a section below the one where the shared variable is created.
-LB