I have a colum of values, from which i need to find the minimum. However i
only want it to refer to those which have a specifc value in the adjacent
column. i.e.

A B
1 3 1
2 2 1
3 5 2
4 6 2
5 4 3
6 1 1

Minimum for "B=1" 1
Minimum for "B=2" 5
Minimum for "B=3" 4

Thanks in advance