Hi RITec,
Steps to use:
1) Enter Visual Basic Editor. You said you know how, but ...<Alt> <F11> is the keyboard shortcut.
2) Once in VB Editor, from the menu, choose: Insert - Module.
3) Go to the Tek-Tips posting by using <Alt> <Tab> (Hold down <Alt> and hit <Tab>
4) Highlight and Copy the routine I posted previously. This starts below the line "Here's the routine..." and ends at the line above "I hope this helps". (The routine consists of the opening routine (Get_Workbook) and two subroutines (Sheets_ChangeFormula and OtherWorkbooks_Close)
5) Go back to your Excel VB Editor screen - using <Alt> <Tab>.
6) On the right-side of the screen, Paste the VBA routines you just copied.
7) Make the necessary modification to the line in the "Sheets_ChangeFormula" subroutine that refers to the location of the formula you need to change.
i.e. Range("J1"

.Formula = "=IF(I107,1,0)"
Note: I had commented-out the last line of this routine... 'ActiveWorkbook.Save
I had intended to delete this, as the file is saved in the opening routine with the line:
Workbooks(wkbk_change).Close SaveChanges:=True
8) Exit the VB Editor - by using <Alt> Q
In my previous posting, I had suggested you use a "keyboard shortcut" to activate the routine - for each time you want to choose a file.
To assign the shortcut, use:
a) Hold down <Alt> and hit <F8>
b) With "Get_Workbook" highlighted, Click "Options"
c) Under "Shortcut key", enter a (lowercase) "w".
Note: If you happen to have your "PERSONAL.xls" workbook open (even if you have it hidden)... After step "a)" above, you will need to change "Macros in: All Open Workbooks" to "Macros in: This Workbook". (see center-bottom of the Macro window).
Then click on the "Get_Workbook" routine.
Then click on "Options".
Then under "Shortcut key", enter a lowercase "w".
Click OK, and close the Macro window.
Save your modified file.
You can now begin to modify each of the 12 files, by holding down <Ctrl> and hitting "w". You just need to choose the file, and the macro will do the rest.
You only need to re-activate the macro each time you want to choose another file.
I hope this further explanation helps.

Please advise as to how you make out.
Regards, ...Dale Watson dwatson@bsi.gov.mb.ca
P.S. I'll be out-of-town for the next week, so if you require further help before I return, perhaps someone else can assist.