SUMPRODUCT to total dates from multiple worksheets

[mtnovak2]

Hi all-

I have been brought in to alleviate human error in counting the total monthly tool repairs entered into a spreadsheet.
In the whole workbook, I have tabs corresponding to all letters of the alphabet plus frequent customers (30 sheets in total). This is used for documenting the tool repairs we take in and then send out by putting the date in, in one column, and the date out, in another.
My goal is to total all of the dates-in and all of the dates-out on a TOTALS sheet to get our monthly repairs in/out totals.

As of now I have columns with the first (column J) and last (K) dates of the month for the criteria in the formula. The dates-in are in column B and I have renamed them all as: DATE_IN_1, DATE_IN_2, etc.
I have already successfully done this for our 4 largest customers using:
=SUMPRODUCT((ATMI!$B$2:$B$603>=J2)*(ATMI!$B$2:$B$603<=K2))
(ATMI is one of the 4 largest tool repair customers)

I want to recreate this formula so that it counts not only ATMI and the 3 other sheets, but all 28 other sheets in the workbook.
The problem is that the formula I currently have for each month does not count all of the dates in all of the worksheets.
The formula I have looks like this:
=SUMPRODUCT((DATE_IN>=J2)*(DATE_IN<=K2))+((DATE_IN_2>=J2)*(DATE_IN_2<=K2))+((DATE_IN_3>=J2)*(DATE_IN_3<=K2))+((DATE_IN_4>=J2)*(DATE_IN_4<=K2))+((DATE_IN_5>=J2)*(DATE_IN_5<=K2))+((DATE_IN_6>=J2)*(DATE_IN_6<=K2))...etc for all the sheets.

The file is here:
TOOL REPAIRS.zip

Could anyone help me out?
Thanks

[oeldere]

Why don't you put all data in 1 worksheet.

Then you have a table and you can use pivot table.

[mtnovak2]

I need to keep all of my customers in different tabs for other monthly reports, plus there is too much data to be neatly organized in one worksheet.
Is there a way I can use pivot tables with different tabs? Or integrate multiple tables into one? If that is the easiest way to do it?

[mtnovak2]

I originally did not know you could attach files to threads. Here is the file that I am still working on fixing.
Thanks for the help.