No you can't cut into cables or use splitters as each serviced Box needs to send switching commands to the LNB.
So, you need an LNB with sufficient outputs to feed all your Boxes.
One feed per Tuner, so eg a
Sky+ Box requires 2 feeds.
LNBs are available in single, quad and octo output.
If you need more, the approach is different: You would need a Quattro LNB and a Multiswitch.
PS: Just noticed you are in the USA .............. No
Sky via Satellite there! Am I missing something?
Actually, it says US, so USA is a guess: I suppose you could mean the United States of Europe ?