Okay,

I have three columns, A B C

A holds multiple occurrences of once appearing data in B.

eg

A B C

10
10
10
10 10 5
11
11
11
11 11 6


I need a script that will read A, find that value in B and paste corresponding C value in D.

So for the above example D would be

5
5
5
5
6
6
6
6


I don't know where to even start.

HELP!