Dragging formula, change sheet reference, but not cell reference

Hello,

Is there a way to drag a formula to the point where I can freeze the cell reference, but change the sheet reference. I know that to keep a constant cell reference, I can use the dollar sign, but I want m formula to change the sheet reference so that I can just drag the formula across. For example, I have the months Jan-Dec listed across in a spreadsheet from cell B1 to N1. In cell A1, I have "Totals" where each month will reference the total in cell B20 on each month sheet. The totals are in the same column on each month sheet. So for January in my summary sheet, I want to be able to say =JAN!B20 and then drag this formula across for the other months, but have the sheet reference change while the cell reference stays the same. Is there a way to do this?