Satelite tv question:

Can I use the LNB from a Dish Network dish on a Directv system? Reason: I recently purchased a tivo receiver for my directv, but am using an old dish which has a single LNB. I previously used, and still own, a Dish Network dish which had a dual LNB. I need the dual LNB for the tivo unit (cannot watch a program while recording another without dual LNB). Will the Dish LNB work with Direct ? Thanks in advance.