Hi TBMIS,
I hope Mr Petty might give you an idea to construct your sandwich:
http://www.youtube.com/watch?v=P_Tqt_rzEfQI suppose your routine is for a single selection. Another option could be to construct it for double or triple selection so the many sandwich reveals will make sense. (Your patter could be about monkeys. How you want to find the monkey that stole the banana and have the spectator sign one of the selection "BANANA" and it will be the last one you reveal) --- [I just thought of it.]
Too many sandwich effects I see are just
"The card gets trap in between the two jokers (or whatever)"
"The card jumps"
"The two cards catches your card (again)"
Sandwich is a beautiful effect and I have always loved it.
The impression it gives me is that it is a card penetration. Either the selection penetrates between the two cards or the 2 cards penetrates through the deck.