Maybe a little semantics going on here. There are 2 areas where you can specify IR or RF. With your software, set SYSTEM PROPERTIES (under home) to IR. For the DVD you want to control by RF, set it's DEVICE PROPERTIES to RF (this assumes that all the source IR codes are located in this device). The remote will send each individual code by either IR or RF, not both at the same time. You can however, still have both IR and RF codes mixed in a macro.
The extender receives RF from the remote, converts it to IR and transmits the IR signal. It does this both as an "IR Blaster" and through the dual emmitter leads. What I would do is connect the emmitter leads to the IR window of your RF DVD and then use tape over the top to mask the IR window. This blocks the signal when controlling the other DVD.
There CAN be some issues with setting up your ccf (where the source codes are located). But these can be ironed out and the system works quite well.
Gotta love them Rams huh? Sorry couldn't resist.
Jim L