Macro to create sum formula across all sheets except one activated in

Hello all

Let me give some background. I have a summary tab that will be in about 200 workbooks. The summary sheet is independent in each workbook but all tabs are exactly the same throughout all sheets and all workbooks..

I am looking for a macro that will create a formula that sums across all the tabs in a single workbook. Each summary page has 6000 cells that need to be summed and the remaining cells need to be untouched since there will be formulas sitting in the summary tab that is based of the summed numbers.

e.g. for one workbook that has 3 tabs SRC RCS and CRS and Summary, I want a macro that will put =sum('SRS'C!20!+'RCS'C!20!+'CRS'C!20!) in C20 of the summary tab. I want the macro to work as a range so that it will create this sum formula for C20:Q20 and create the formula for the corresponding cell in the rest of the sheets.

Is this possible? I've been racking my head and can't think of anything.