2 mirrored external displays

Ok so heres my vision. That new wireless keyboard looks like it would be great to sit on my lap and use my mac on my 40 inch tv while i lounge on the couch.

So heres my setup, I have a Core 2 Duo MBP with ATI RadeonX1600 and I run an additional display (a dell 2007wfp) in extended desktop mode. Both displays run 1680x1050. What I want to do is split the dvi-d port on my MBP so I can mirror the external display with my HDTV.

I bought this:
http://www.cablesunlimited.com/products/Prod_Individual3.aspx?groupcode=I3583

but basically it doesn't work. If you just plug in the HDTV to the HDMI port and leave the DVI port open it works fine and if you plug in the DVI and leave the HDMI open the dell will only come up at the lowest possible resolution, 640x480 (gross). When you plug them both in nothing comes up on either.

Anyone have any idea how to do this? I would even settle for a simple cheap switchbox to switch between the dell and tv but i cant seem to find one.

Anyone have any idea besides just unplugging one and plugging in the other everytime i do this.

Thanks,
James

 

http://www.markertek.com/SearchProduct.asp?item=DVIAB-1&off=0&sort=prod

anyone know if something like this will work in reverse? I mean all it is is a switch so it should work right?