I have two column, Column A contains 6000 random values. Contain B will be a
subset of Column A which is equal to every third value of Column A (as
illustrated below). In other words, Column B will be in total 2000 values. Is
there a way I can get Column B read Column A value automatically? Thanks a
lot!


A B
1 3
2 6
3 9
4
5
6
7
8
9