entering values by comparing two sheets

Hi,

First I would like to apologize if this has been answered before but I was unable to find a thread (probably because I was searching wrong)

I have two spreadsheets that I would like to compare.

first sheet I generate from my local database and has the following collums:
A Invoice#
B PO#

second sheet sent to me has
A Invoice
B PO
C Order#
D Acct #

what I would like to get is a formula in Sheet 1 in the c collumn that will enter the Order number from sheet 2.
the problem is that they are not in the exact same order so i would need the formula to do a type of search.
in plain english it would be: find the invoice# from sheet 1 in Sheet 2, and return the order number from Sheet 2 into sheet 1

I know this is not that hard to do but I am probably overthinking it and just cant get the formula to do what I want.

Please help!!!

Thank you

RockerGal

Try

In C2 of Sheet1 with invoice number in A2

=VLOOKUP($A2,Sheet2!$A$2:$D$100,3,0)

OMG THANK YOU SO MUCH!!!!
I really was overdoing it!!
I was doing index and match codes and just ended up confusing myself!

thank you thank you thank you thank you!!!!