IF Formula that results in Protection?

I was wondering if there was a way to write an IF formula that results a range of cells to be protected? In other words, if A1 = 500, then B1:B10 would be protected? I also heard there may be a way to format a cell to where you could have a formula in, yet still be able to key punch in it, without having to erase the formula in the cell. This too would satisfy my needs. Any truth to it? If someone could answer either of my inquiries, I would appreciate it. Thanks!