selection screen problem

Hi ,

I have a selection screen which consists of 2 select options say 'A' and 'B'.

the low element of A i.e A-low and B-low are associated , so when i give f4 help on A-low even B-low is automaticalyy populted which is fine.

Now when i give F4 on A-high , A-high and B-low are populated , but i want A-high and B-high to be populated....any suggestion why is this happeneing