Welcome to the Board!
I think we will need a bit more information in order to help you. But I would caution you about using the "multi-value" field data type. Though Access starting allowing it a few years ago, I would recommend avoid using it, if you can. It really kind of violates the rules of data normalization,which can be problematic for relational databases. And other relational databases, like SQL and Oracle, do not allow this sort of thing. So if you ever needed to convert your database to SQL at some point in the future, you wouldn't be able to do so without redesigning stuff and fixing up the data.
There are usually other, better ways of handling it, usually by making another table that has a one-to-many relationalship with the main table.