I'm thinking this isn't possible, but thought I'd float it out to see if
anyone had any ideas. I have the following columns of data (an excerpt;
there's about 300 records in my table):

TimeID Num1 Num2
1 4 4
2 5 4
3 6 2
4 5 3
5 3 3
6 4 4
7 4 3
8 6 2
------------------------------
9 5 4


Is there a single formula that can:

1) find the most recent values for each, unique Num1 (e.g. for Num1=6, it'd
be TimeID=8),
2) See if any of the correlating values to the Num1 values in Num2 from rows
1-8 (not 1-9) match the most recent entry in Num2 minus 1.
3) Sum up only those values in Num2 (rows 1-8) that are from the most recent
values in Num1 whose correlating values in Num2 equal the most recent entry
in Num2 minus 1.

So, in the excerpt above, the cell of this magic formula would return a
value of 9, if you can follow this.

I'm not holding my breath, but there you have it! Thanks a bunch in advance!