This is possible if you have either the Slingbox PRO or the Slingbox PRO HD. You only need to set a splitter on the cable that comes from the wall.
Then, send two lines (one to the STB and the second to the Slingbox). This way, you will be able to watch a different channel without affecting to home viewers.
The only disadvantage for this layout is that you will only get the basic channels on your Slingbox.