|Now comes day 3 and it's updated but the formula needs to recalculate based on this update.|
What is It's?
If you have:
A B C
1) $10 $5 $5
With the formula =SUM(A1-B1)
in cell C1,
Any changes in A1 or B1 will automatically be recalculated in cell C1,
unless you have turned off the Auto Calc functions.
Or perhaps, because you have imported your data and Excel interpreted the data as Text not Numbers.