plz reply its urgent.

hi,

I have one issue i:e I have one selection screen with fields company code and plant.If i give plnt as m001 and company code as 'renl' then display two more selection screen input fields verna and ' vernr' and after giving this i have to display all these things .how can i hide these 2 fields on selection screen?any body send me sample code.plzzzzzzzz.