I am sure this is an easy task, but at the moment I don't know where
to start.
I have an excel file with 2 tabs. In tab 1 I have 580 lines with
numbers:

Col1 col2 col3
1 80074635
2 80073639
3 93648329
..
..
..
580 80038938
============
In tab 2 I have 560 lines:

Col1 col2
1 80083476
2 80037363
3 83630923
..
..
..
560 89237383

===========
I want col3 in tab1 to have the value/text "YES" if the corresponding
number in col1 in tab1 exists ANYWHEREin col2 of tab2. If not the text
should be "NO"

What should I use to do this and how?
I am not so experienced in Excel so would appreciate to-the-point
solutions.

BH