PopUp Box with Multi-Selections

[DBFIN]

I need to create a popup box in a form that would allow one to select multiple states. The selected states would be output to the "state" field in a table. Combo boxes only allow selection of a single state. How can one select multiple states that are output to a table ?

 

[DBFIN]

The file attachment below provides a view of the relevant parts of the database.