I would recommend setting up a seperate db for RS. If you installed RS with the MS best practices you most likely didn't set up the installation with a RSExec...

Also in RS if using an IIf statement as a formula (like excel):

example: =IIF(SUM(Fields!Col.Value + Fields!Col2.Value) > 0, ((SUM(Fields!Col1.Value) - SUM(Fields!Col3.Value) - SUM(Fields!Col4.Value))/ Fields!Col3.Value)

If you need to export to excel...