I'm not sure that I understand your question fully. What I think you are asking about is if you can run a single cable from your dish that carries both LNB's signals from your dish.
A multi-switch will not do this. A multi-switch allows you to separate a single LNB's signal into multiple cables so that you can feed multiple DirecTV receivers.
There is something called a stacker that does something similar to what you are looking for. Most people seem to use these for inside runs when putting in a new cable isn't practical. I don't know whether you can yse these outside. You can find info on that at www.tivocommunity.com in the DirecTV with TIVO area.
Note - they make a dual cable for long runs from the dish. This is fairly inexpensive so I recommend going with that if you can.
Note - the reason you have to run two cable up to the dish is that DirecTV uses voltage differences on the lines to differentiate between odd/even channels. Therefore, combining both LMB's on one cable doesn't work.
I recently purchased a Directv Tivo, the problem I have is my dish is a significant distance from my house. Is there any way to hook up both tuners in a Tivo utilizing a diplexer or multi-switch to two LNB outputs on a directv dish?