for for updating database with referential integrity

Hi:

Here is the essence of the problem:
I have created an Access database that I want the fire chiefs to update. The database is a one to many structure with referential integrity set. One fire truck has many capabilities. So if Fort Myers has a truck named 'FM101' and it has several capabilities such as 1.) pumper, 2.) extrication 3.) Advanced Life Support.

My problem is how to set up a form to do that. In particular, how do I set up the form so that it will allow the fire chiefs to input several capabilities at a time for a truck.

I can build a form showing the truck which was obtained from a pick-list. And I can show another field showing a pick-list for the capability of that truck (pumper, extrication, ALS, etc). My question is how do I set up the form to allow the chiefs to input multiple lines for the many capabilities of that one truck? Right now I have one input for the truck and one input for the capability - but I want to enable the user to input as many capabilities as they feel necessary.

How do I do that?

thanks