Table of customers
Table of "contacts with customer" via customer ID
Table of Actions via "contact with customer" id

Proper connection?
You mean bound or unbound?

You could have this on one form or several forms.
The topp section would deal with the customer (use a search option to list those already on record and select on (which then holds the id) or create one (which returns an ID). Option to use a pop up form for data entry. Use a couple of labels for the selected Customer.
Second section could be a list box with all the contacts of that customer so far (empty initially). Button to add a new contact, which goes to a pop up form for data entry. When the form closes the list box is updated and displays the contacts. Use a select option again or just the highlighted row to refresh the third section. Another list box which holds all the actions for the selected contact. Pop up form again.


Or you could use a tabbed form, three tabs with the same options as above, but no pop ups as you could put each of the controls on the tabs.

Or three forms Linking to each other (one opens the next etc...)

Just some options there are loads out there, and you wouldn't need to go into creating an Active X control unless you were going to use this inside another form of som sort? Making life more difficult?