Crystal Reports Sub report , shared variables etc

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   Frustrated, and ready to quit!!
I have created two reports in which both i have had to manipulate a field to be able to have a unique field which can now be common in both. (Ie Process id). 
One report shows paid, the other remitted; both are based on parameter date range.

I would like to now collate the two reports, that is show them as one single report and then group by process id in order to calculate the total paid and remitted per process id.

I have placed the paid report in Detail A section and remitted report in Detail B section , i would now like to ammalgate the two in Detail C section do a group by and summary. Is this possible. 

The result may be such that there are paid with no remittances and remittances with no paid, therefore i need a full outer join to ensure all records are captured in the Detail C section.

I appreciate some directino on this issue, as conceptually it sounds easy but implementation is driving me crazy!

Thanks again in advace