Need to have 2 fields that pull from the same related table on 1 form

thanks!

Quick question.... which of the 3 tables should be used for actually creating the trip? I think this is where I'm getting tripped up.

Well, you would first set up the installation record, and then add Assigned Installers.

If you edit the Avpdvanced table properties for installations to check the box for save automatically when a child is added, that will be a smoother process

But which table is actually being used to record the info? the installation or the assigned installers?

Well, both.  The Installation record is about the trip and maybe what is to be done that day for the job, and the child table is which installers are riding in the truck.