<<Do you have any suggestions re a method to mimic a button "hold"? >>

Yeah, hold the button! :) If the button on the URC-8200 doesn't repeat properly, it probably means the device code is using the wrong protocol. You might want to try some other device codes and see if you can find one that works properly. If you want the techie details, here they are: your device is probably expecting a signal that uses the NEC2 protocol, where the whole signal is repeated when a button is held down, but your remote is probably using the NEC2 protocol which only sends the signal once and then repeats a special two byte code if the button is held down. If you use the NEC1 protocol on a device that is expecting NEC2 it will work, but the repeat function won't.

For example, I found that VCR code 0240 worked my Samsung SV5000 VCR, but the buttons didn't repeat. VCR/0240 uses NEC1, the VCR expects NEC2, so I have re-worked the code using NEC2 and added it to my remote and now it works fine.

<<Can this function be programmed into the EPROM using your interface?>>

Yes, if you were using the 15-1994, but I haven't taken the time to decode the memory format for the Producer 8 remotes yet. I am not familiar with the URC-8200, so I don't know if that's similar to a Prod 8 or a Cinema remote.

Rob.