Yes, this is possible. You'll need to create "Shared Variables" to do it.
You'll have to do something like this (you'll probably have to tweak this, and Brian may have a better answer...).
Formula in Main Report
Shared Numbervar Total1;
//Initialize at start of report
If previousIsNull({table.some key field}) then Total1 := 0;
Create a similar formula for Total2. Create another formula to add them together.
Formula in Subreport 1
Shared Numbervar Total1;
Total1 := Total1 + <whatever you need to do to get Total1>
Do the same sort of thing with Total2 and Subreport 2.
In order to get the correct result, you'll probably have to put your formula that adds Total1 and Total2 in a group or report footer.
-Dell