OK - Welcome to the forum.
You must have some fields in your main data source, under data fields that you want this data stored. The user will choose a contact state and then the contact and this will get placed in the data to be submitted to Access. Correct?
You do not really need to create another data node in your main form.
Typically you would just make the field you want to store state in, from your data fields, a dropdown control in your form.
Then have the source be the list of states from your secondary connection.
Then put a dropdown on contact name and this would use the secondary list but with a filter where state = the state chosen in the drop down (the state field under Datafields) This would then allow them to pick the contact they want.
Then have a rule which would populate the rest of the fields based on the name they had chosen, such as phone or whatever.
Email me if you would like to see an example.