[ACCESS] List Item values based on Current Form Data

[NPassero]

I have a List Box on my form in Access, and I want to update the list items based on a query and based on the values of the current record.

in essence the query would be:

SELECT GroupName from GroupMembersWHERE GroupMembers.ContactID = Form!Contacts.ContactID

I would assume that this goes in the AfterUpdate event? but I am very unfamiliar with VB Script and also Access programming and am not sure how to fill the item list