Sorry, I should have added that I don't want to protect the sheet. Reasoning is that ocassionally we want to overwrite the formula for some special reason. Weeks or months later, someone opens the worksheet and revises a couple of numbers, but they forgot they overwrote one formula so now things aren't calculating correctly.
When might this happen? We're competitively bidding a project and add a certain percentage to the estimated costs for our markup to get to our TOTAL BID. When we need to give our bid breakdown, we want our fee spread proportionately throughout the breakdown, but we also want all numbers rounded to nearest dollar. If numerous numbers are rounded down, the breakdown doesn't match the TOTAL BID. Therefore prior to distributing the breakdown, we change one or two numbers manually. I want to be able to easily see what numbers I manually entered over the formula.
So, I was wondering if someone might know of a way to write a conditional format, that if the cell didn't contain a formula, I would get certain formatting.