I have a list of timestamps in column A (one per minute for a day,
total 1440 entries), and an associated list of TRUE/FALSE values in
column B:

12:00 AM FALSE
12:01 AM FALSE
12:02 AM TRUE

Try...

=INDEX(A1:A7,MATCH(2,1/(B1:B7=TRUE)))

....confirmed with CONTROL+SHIFT+ENTER, not just ENTER.

Hope this helps!

In article ,
Greg wrote:

I have a list of timestamps in column A (one per minute for a day,
total 1440 entries), and an associated list of TRUE/FALSE values in
column B:

12:00 AM FALSE
12:01 AM FALSE
12:02 AM TRUE
.
.
.
11:56 PM TRUE
11:57 PM TRUE
11:58 PM FALSE
11:59 PM FALSE

I need a formula that will return the timestamp associated with the
*last* TRUE value in the list. In the example above, the formula
would return 11:57 PM.

If there are no TRUE values anywhere in the list, then the formula
should return some error text, i.e., "No TRUE values found."

The spreadsheet has no macros on it, and I would prefer to keep it
that way (so users do not have to contend with macro virus warnings),
therefore a formula-based solution is highly preferable.

Thanks,
Greg Hurwitt