Click/drag a formula pulling from differ sheets w/ excel auto changing sheet names only

Hi!
Here’s what I’m trying to do. I have a budget workbook. In it, I have several worksheets and need to pull data from them into a summary sheet I’ve named “Dashboard”, the 1st sheet. The exact information for the month in the same exact cell throughout all of the Monthly Expenditures worksheets.
Worksheet Names
Sheet1 = Dashboard
Sheet2 = AUG EX
Sheet3 = SEPT EX
Sheet 4 = OCT EX

And so on…
So, I know the formula I need to pull data from one sheet to another. It is as follows:
=SUM('AUG EX'!$D$20:$E$20)
The problem is that I would like to be able to click and drag the formula down where excel automatically inserts the next worksheet name as I drag/copy to the next cell. I actually have to do this several times and don’t really want to have to go in and change the sheet name for each one manually. Can anyone help? Is it possible? Or maybe you have a different way to accomplish what I need?

Month Total Monthly Expenditures
August =SUM('AUG EX'!$D$20:$E$20)
September =SUM('SEPT EX'!$D$20:$E$20)
October =SUM('OCT EX'!$D$20:$E$20)
November =SUM('NOV EX'!$D$20:$E$20)
December =SUM('DEC EX'!$D$20:$E$20)

Hi FDibbins,

It worked! Thank you so much. I've never used the INDIRECT function before. Learned something new.
Also, thank you for the welcome.

Warm Regards,
Cilla