Excel forumla/? Help

Hi,

I need some help figuring out a formula, or a way of calculating something.

I have 2 excel workbooks.
I need to figure out how to get a value in Column A of workbook 2 based on the following.
Column B in workbook 1 contains figures, i need to match these figures from the ones in column B in workbook 2 and if they match, have the value that is in the same row from column A in workbook 1 to be input into the corresponding cell/row in column A in workbook 2.

I'm not sure what i have to do to get this to work.

eg.

workbook 1

A B
1 36
5 37
9 38
2 39
9 40

Workbook 2

A B
36
37
38
40

i need to match the figures and then input the value from wb 1 col a into wb2 col a (i have over 4000 rows which is why it would be faster if i didn't have to do this manually)

Thanks