Interesting. You could do it the brute-force way
(=IF(AND($AC$136="Yes",$AC$137="Yes"...),"Yes","No "), but that would be
ridiculous if there were more than a handful of them. Let's see...

Oh, of course. Try COUNTIF, to count how many "Yes" values there are in
$AC$136:$AC$146, and if it's 11 say "Yes", otherwise "No". Like this:

=IF(COUNTIF($AC$136:$AC$146,"Yes")<11,"No","Yes")

If the size of the range might vary, get the formula to use the ROWS
function to count how many rows there should be:

=IF(COUNTIF($AC$136:$AC$146,"Yes")<ROWS($AC$136:$A C$146),"No","Yes")

Or name the range and then use the name:

=IF(COUNTIF(Flags,"Yes")<ROWS(Flags),"No","Yes")

--- " wrote:
I can't get this to work:

{=IF(($AC$136:$AC$146="Yes"),"Yes", "No")}

I want to return the header of data to return Yes once all the details
have been flipped to yes.

Thoughts.