dropdown

hi,

i have a adobe acrobat from. there r 2 drop downlist. One is A, another is B. A has items- AA and BB. and B has items- A1,A2,A3,B1,B2,B3.if i select AA from A box, then i want B box only give scope of selection only - A1,A2,A3 but B1,B2 B3 will not show in dropdown.if i select BB from A box, then i want B box only give scope of selection only - B1,B2,B3 but A1,A2 A3 will not show in dropdown.

can u pls help me?

thanks

Ali