Filling formulas with specific cell references remaining the same

[quinxorin]

I need to fill a formula in a range of cells downward, specifically the
formula IF(OR(O2=U1,P2=U1,Q2=U1),2-L2,0), with the U1 cell references
remaining the same, continuing to refer to U1, while the other cell
references (O2, P2, Q2, and L2) change and fill normally. Conversely, I need
to be able to fill the formula right with U2 being the only reference that
changes. Is this possible to do? If so, how? Doing this manually would take
several hours. I am using Excel 2007.

 

[quinxorin]

Thanks. I tried all sorts of symbols, like single quotes, double quotes, and
paentheses, but I never thought to try the dollar sign.