Here are the steps to program a button on your Comcast silver remote. Once done you can learn the code to your URC remote.

Here is the exact procedure to program a 30 second skip to the remote.

1) Press the "Cable" button at the top of the remote to put it into Cable Box control mode.
2) Press and hold the "Setup" button until the "Cable" button blinks twice.
3) Type in the code 994. The "Cable" button will blink twice
4) Press (do not hold) the "Setup" button
5) Type in the code 00173 (for 30 second Skip).
6) Press whatever button you want to map the skip function to. (I mapped mine to the FAV button)