If I understand you right, here is what you getting at:
If Cell A is not empty, then cell B of the same row is to equal Cell C of
the row above it.
Not only that, you also want to have the formula in the B column to be
locked.
First, Under the assumption you are starting at row 5, in cell B6, put in
the formula of:
=IF(A6="","",C5)
Copy that formula from B6, and paste it on down as far as you need to.
Select the entire worksheet, and then press Ctrl-1 (Format Cells)
Go to the "Protection" tab and checkmark "Locked" and "Hidden" (if you want
the formula to be hidden as well)
Now select the cells you want to have unlocked, and press Ctrl-1 again.
Uncheckmark the "Locked" option
Now protect the worksheet (may password protect it) via Tools, Protection,
Protect Worksheet (Alt, T, P, P) Yes, I do use that quite a bit with my
work.
Granted, the protection stuff in Excel won't protect against the determined
people, but it will at least protect from the casual people (which are most
people).
--
Thanks,
Ronald R. Dodge, Jr.
Production Statistician
Master MOUS 2000