Buy a second RFX (or two) and turn off the front blaster.

Then set up the interface on your pronto for the cable/sat/whatever box.
Set the RF address code for one.
Now Copy and paste it into your system.
Now you should have 2 of them.
Set the RF address code for the second one to the RFX.

Tada... discrete control of two boxes with only one address code. Sure it cost $400 in RFXs... :). BUT IT WORKS!

The above is why we started using RTI but its RF processor cost more then 2 RFX6500s.