dwayne,
The IR Commander (UX17A), VCR Commander(UX21A) or VCR Commander II (UX23A) have to be setup with X10 Commander software before you can use the RF codes..
roger1818 is correct, you need a CM17A firecracker to run the X10 Commander software that will allow you set up the IR/VCR commander. I have the X10 Commander software on an old Win98se box, if I remember there are issues with X10 Commander and XP.
Once you have the IR/VCR Commander setup for the devices you want to control (TV, CD, VCR,DVD), you can use the CM15A to send the RF commands. You must use the "Old RF Remote Commands" ie: 00TV, 03Power, 01MUTE....
ahcmd sendrf e1 00TV (selects the TV device)
ahcmd sendrf e1 03POWER
ahcmd sendrf e1 01MUTE
Make sure you include the 2 digits at the beginning of the command, that one bit me for awhile.