Combining FBL5N & FBL3N to get the Final amounts in a report

Here is what we want to do:

1. Run FBL5N with certain selection criteria to get Clearing Documents for invoices.

2. Put these Document numbers in Dynamic selection screen field of FBL3N Document number to get G/L data for those documents.

The problem we are having is: FBL5N run gives thousands of Documents and when we run FBL3N with that Selecion, we essentially get a Short Dump.

Even with a much smaller number of documents, the process is very very slow.

My questions are:

1. Is there a better way to get this info?? Essentially we want the information that FBL3N gives from selection with FBL5N?

2. Can we speed this up in case this is the only possible way??

Thanks.

Lukesh