Hello TED,

It's easier if you can describe in words what you want to do rather than post a formula that doesn't work.

If you want to find the closest value in AF15:AF380 to the value in AA15 then perhaps

=INDEX(AF$15:AF$380,MATCH(MIN(ABS(AF$15:AF$380-AA15)),ABS(AF$15:AF$380-AA15),0))

confirmed with CTRL+SHIFT+ENTER

If there is a value equal to AA15 in that range then it'll return that, is that what you require?