Lookup Loop

I have a need for a simple Excel macro to do the following:

1) Loop through the rows of TabA
2) Search TabB for the value in columnB in TabA
3) For each row hierarchically below the matches copy the value and insert under the value in TabA

the no. 100201002010001600 is found in TabB but
100201002010001590, 100201002010001580 these no. Not found in TabB
Please tell about that No. which will not in TabB.