I built a function some months ago, which works perfectly.

The difficulty is that the entire text in the cell is bracketed by "curly
brackets" ( { and } ). When I modify anything in the cell, those brackets go
away and the formula, even if I haven't actually changed anything, no longer
works.

I vaguely recall that there was some special keystroke combination or yoga
position I had to use when saving the changes in the cell, in order to not
disturb the curly brackets, but I cannot recall what they may be.

Here is the content of the cell when it's working, if it helps any:

{=SUM(IF(AF$4:AF$4000="A",IF(X$4:X$4000="Y",IF(AC$ 4:AC$4000="DM",AE$4:AE$4000,0),0),0))+SUM(IF(AF$4: AF$4000="A",IF(X$4:X$4000="I",IF(AC$4:AC$4000="DM" ,AE$4:AE$4000,0),0),0))}

Thanks for your help!!!

-DJW