To avoid duplicate values in DrowpDownByIndex

hi

Iam calling an RFC ,it's output is as following

column 1 column2

A 2

A 3

A 42

B 34

B 3

B 11

B 0

Iam displaying these values in two combo box. But my requirement is as following in first combobox if i select A ,only those values in column 2 which are mapped to A ie(2,3,42) should see in the combobox two.So pls help me i don't know how to do this iam a beginner in webdynprofor java.

I'll give points.......