Prior to departure.... the fee is what the fee is. Any changes are fee plus fare difference.
I think I clearly understand what you're trying to do, and the answer should be NO.
Example....
Booked Aug 2 outbound, Aug 10 return.
Want to travel Aug 1 outbound, Aug 10 return.
Even with showing up to the airport Aug 1, because it's not "SAME-DAY" for your ticketed itinerary... the "at airport" same day changes won't apply and you'll be stuck with the before departure change fee plus any additional fare.