I have a situation I've never run into. I have a simple equation like =C1-D1
located in cell A1.

I want to copy this equation from A1 through A100. I can use Autofill to do
it and it would update the cell reference from C2 to C3 to C4 etc.

But what I want is that as I copy the equation down, the column references
would update rather than the row references. So as I copy from A1 to A2, the
equation would then read =D1-E1.

Any help would be appreciated.

-Eric