Have this formula: =MAX(DAYS360(R24,U24),0)

Now I need to add this:

Even though this is totaling the days bewtween R24 and U24, if I put a date
in S24 (this would override U24), I want the formula to total the days
between R24 and S24.

I need to keep the date in U24. It is the original work date. S24 would be
a revised date.