I have a spreadsheet with 4 columns : A, B, C, D.

I want to calculate the difference between A-B and C-D.

So in cell E2 I enter the formula =A2-B2 , and get the result that I want, which is the difference between A-B.

Now I drag the formula in E2 to cell F2, expecting that Excel will think that now I want the difference between C-D.

However, when I drag the formula from column E to column F I get =B2-C2. My question is: how can I make Excel “understand” that I want to use =C2-D2 after =A2-B2, and NOT =B2-C2?