I have been struggling for a few days with this problem and still can't
find a solution...
This is what I am trying to achieve:
1. Find another cell in column 2 with the same value as starting cell
located in the same column 2 (not second, not third and not last same
value, there are going to be just two cells with the same value and I
am looking for that other one).
2. Check value from column 3 corresponding with that cell,
3. Return this value into column 4 at the row of the starting cell.
I don't think that I am doing a great job explaining it so let me put
an example.

Referring to data shown below:
6 teams are paired in a tournament. Pair numbers are being recorded in
column 2. Column 3 represents points gained by each team and column 4
(this is what I am looking for) is supposed to show points gained by
the opponent - another team from the same pair (same value in column
2).
Starting at cell A2:
A2 value is 1 and another cell in this column with the same value is
D2. Points gained by team 4 (row D) are represented in corresponding
cell D3. I would like this value to go into the A4 cell - and represent
points gained by the opponent.
Same problem for other cells - starting at E2 I would like to insert C3
value into E4 cell.

1 2 3 4

A team1 1 A D
B team2 2 B F
C team3 3 C E
D team4 1 D A
E team5 3 E C
F team6 2 F B

I have tried LOOKUP and VLOOKUP but column 3 values are not going to be
sorted and I was not able to (for example) exclude the row, at which I
start my formula. I am clearly no able to come up with a complex
procedure that would do that... Please help.