I see the question was posted previously but the answer didn't help me so
maybe someone can help.

I have a worksheet with dail weights broken down by week e.g.:
C1 Beginning Weigth
B3:B9 Dates (week 1)
C3:C9 Weights
F3:F9 Dates (week 2)
G3:G9 Weights
etc.
After all the entries I want to have a "Monthly Gain/Loss" cell.

I hope this is clear
TIA