Is it possible to select more than one option from a drop-down list within
the same cell? How would you set that up?
As Jeff says... is this an Access question?
If so, and if you're trying to store multiple values in one field... DON'T.
A2007 has a "multiple value field" misfeature if you're willing to make your
database nonstandard and hard to maintain, but that is not how relational
databases are designed to work.
What is the data, and how do you want to use it?