I recently started experiencing a problem I have never had in Excel
before, and I don't know if it has to do with an Excel setting in
general or if I screwed something up with the Macros I was writing.

I have a bunch of formulas in my worksheets (If Statements, Now(),
Sum(), etc). Let me use this quick example.

C4 = 5
C7 = 10
C8 = Sum(C4 + C7)

If I repopulate C4 and C7, C8 no longer automatically changes. But if
I go to edit C8 (click on it and hit F2) and then hit enter, it will
then update correctly.

Why on earth is it doing that?