Make LCD TV sleep when computer sleeps?

I recently purchased a T27B350 LCD TV and have it hooked up to a computer via HDMI. When the computer goes to sleep, the "no signal" warning goes on the screen. I've set the timer to only show it for 15 minutes before turning the TV off, but I'd prefer it wasn't shown at all. When I'm telling the computer to sleep, I want the screen to go black (just like a normal monitor). Is there a way to do one of the following?

* When the computer sleeps, the screen goes to black instead of showing "no signal"?

-or-

* If the TV HAS to turn off, do it immediately on signal being lost instead of waiting 15 minutes?