On New Record Add Value to Control

Okay, I have 2 bound fields. One called GirlID and one called Last Contacted. I want the date to be entered into this field (Last Contacted) when the user enters a new record. Should the code be On Current or on exit the GirlID control or what ? The control Last Contacted is a date field with m/d/yy as it's format and 99/99/00;0;_ as a input mask.
What do you suggest ?