modify screen???

Hi all,

i have 2 radio buttons.

one for sales and another for purchase.

now if i click sales radio button,

i need to make the s_vbeln is select-options input button to be active and can enter values.

and s_ebeln which is for sales should be disabled.

so similarly,

if i click purchase,

s_ebeln should be enalbled to enter value

and s_vbeln should be disabled.

what to do.

pls help.

will be rewarded