Search Help question

Hi,

I have 3 parameters on my screen,

Parameter A

Parameter B

Parameter C

All which contain OBJIDs from HRP1000 WHERE OTYPE = 'S' (Positions).

However, when selecting a particular position id in Parameter A, this position id should be excluded from search help for Parameter B and C.

How do I do this? Do I use the import parameter for search help? Where do I go from there? Do I need to write a Search Help Exit? If so, how?

Thanks