need help

parameters : r1_g1 type c radiobutton group g1,

r2_g1 type c radiobutton group g1.

i declared two parameters of radiobutton.(i.e in o/p screen we have two radio buttons )my requirement: if i select 1st radiobutton i want " two check boxes" in the same screen.if i select second i want the another parameter name of type c length 20.

can anyone help in this regard.