[Huck]

Run one of your sat. cables. Maybe the one that is labeled cable in the hookup compartment, into the out side of an A/B switch.
Then run your sat. dish to sat. receiver into the A side of the switch.
Run the "cable in" on you video selector box to the B side of the A/B switch.

Then you can switch between cable and sat. by using your A/B switch.