On Sun, 25 Apr 2010 01:24:04 -0700, Joe
wrote:

I got 3 columns in excel. First two is ID & Name, third column is a subset of
the 2nd Column. Now, I want the corresponding ID's for my 3rd column (which
should be looked up in first 2 columns) in my 4th column.

ID,Name,Subset-name,Subset-ID?

Assuming your data are in columns A to C from row 2 to row 100.

In cell D2, try the following formula:
=INDEX(A$2:A$100,MATCH(C2,B$2:B$100,0)

Change the 100's to fit the size of your data in columns A (and B).
Copy the formula down column D as far as you have data in column C.

Hope this helps / Lars-Åke