Autofilling a module name

Autofilling a module name

I created a module "New Module "and would like to autofill the name to read:

New Module Name= Account  Name_Contact Name_Potential Name

I would like to accomplish this by having the name autotfill once I select the 

Account Name via Account lookup field in New Module
Contact Name via Contact lookup field in New Module
Potential Name via Potential lookup field in New Module

I have a workflow rule setup to autofill the name but it will not let the autofill trigger.
When I create a "New Module" and select the three items above from their corresponding lookup fields it will not let me save "New Module" because "New Module" Name is required by default.