if/then formula containing and/or statements

Hello all, new here and have a question I will do my best to put in writing.

I have a column in which the cells may contain 1 or more of the following tags, lets call them A through D for this example:

I want to devise a formula - I'm guessing it's an if/then formula - that does the following: If A1 contains "A", "B" and/or "C" then B1 = "C". If A1 contains "D" but does not contain "A" and/or "B", then B1 = "D"... and so on.

I apologize if this is a lame-o question. I didn't want to get too complicated, but hope I'm providing enough info.

Thanks a lot, Dean