How exactly is your data entered in I and A? If you're using numbers (or
numbers with some type of date), this is fairly easy. If you're using true
text like "Jan 2010". Another assumption is that column A is sorted.
Possible ideas:
=LOOKUP(I2,A:B)
=LOOKUP(TEXT(I2,"mm-yyyy"),A:B)
=SUMPRODUCT(--(TEXT(I2,"mmyyyy")=TEXT(A1:A100,"mmyyyy")),B1:B100 )

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Best Regards,

Luke M
"JEB" wrote in message
...
Totally lost on this one.

I have a date values in Col I that are fed in from another sheet. These
dates may be typed in by a user in any format, but the critical info the
year
and the month.

I have a series of months and years listed in Col A with corresponding
info
in Col B that is only pertinent to that info in Col B. (Col B is the
average
monthly outdoor temperature).

In another Column (let's call it M), I want to "index/lookup" the month
and
year in Col I, match it with the month and year in Col A, and return the
value in Col B.

Any ideas?