Hi Mary.
I had a similar task and I did it just using FI-CA.
I created new payment method for outgoing payments and I coppied the DME file that was used on F110. Then, when running FPY1, I restrict the payments to that repayment method only and create payment medium file using SE38 + SAPFKPY3.
Maybe this document can give you some starting points for this kind of solution: Configuring Payment Medium Formats
Marko