I am building a database in which I want to use a portal that has a similar behaviour to the portal used in the Event Management Starter solution which is displayed on the Events->Details->Contacts tab.

Namely, when clicking on the Name field in an existing or the new record row, a drop-down list of names (if they already exist in the Contacts Table) appears and by clicking on one, it is selected for use in that record. Since the field's control style is defined as a normal edit box and the table on which the portal is based seems in fact just to be a collection of pointers to the Contacts table, I cannot see how this drop down list is generated.

I'd be very grateful for any pointers.

It took a lot of head scratching and not a few deleted expletives but I finally found the answer.

The drop down list was in a field hidden directly beneath another field whose control style was edit box. Evidently a click on the empty edit box was passed through to the field beneath causing the list to display. I didn't even know such behaviour was possible ;)