oracle - how to write when-checkbox-changed trigger -

there 2 distinct checkboxes named chkbox_remove_bill, chkbox_print_bill in same block. user can select 1 checkbox @ time. when 1 checked 1 should unchecked. trigger in oracle forms 6i.

i wrote on chkbox_remove_bill, when-checkbox-changed trigger

declare

val number; 

begin

if checkbox_checked(:blk_remove.chkbox_remove_bill)  val := 0 ; -- replace real unchecked value  --:blk_remove.chkbox_print_bill := 1 ;  

else val := 1 ; -- replace real checked value --:blk_remove.chkbox_print_bill := 0 ; end if ;

begin      if checkbox_checked(:blk_remove.chkbox_remove_bill) <> false          :blk_remove.chkbox_print_bill := 0 ;     else         :blk_remove.chkbox_print_bill := 1 ;     end if ;  end;  exception     when others         call_note_alert('error'); 

end;

i wrote on chkbox_print_bill, when-checkbox-changed trigger declare

val number; 

begin

if checkbox_checked(:blk_remove.chkbox_print_bill)  val := 1 ; -- replace real unchecked value  :blk_remove.chkbox_remove_bill := 0 ;  

else val := 0 ; -- replace real checked value :blk_remove.chkbox_remove_bill := 1 ; end if ;

begin

    if checkbox_checked(:blk_remove.chkbox_print_bill) <> false          :blk_remove.chkbox_remove_bill := 0 ;     else         :blk_remove.chkbox_remove_bill := 1 ;     end if ;  end;  exception     when others         call_note_alert('error'); 

end;

/////// when check 1 checkbox, both selected

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in form there 2 checkboxes named chkbox_remove_bill, chkbox_print_bill in same block named blk_remove. when form runs, user want check 1 @ time (like radio button). how write trigger on when-checkbox-changed ?

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i had changed code, it's working properly

i wrote code on chkbox_remove_bill, when-checkbox-changed trigger. chkbox_remove_bill checked value = 1, unchecked value = 0.

declare

val number; 

begin

if(:blk_remove.chkbox_remove_bill = 0)then     :blk_remove.chkbox_print_bill := 2; else     :blk_remove.chkbox_print_bill := 3; end if;  exception     when others         call_note_alert('error'); 

end;

i wrote on chkbox_print_bill, when-checkbox-changed trigger. chkbox_print_bill checked value = 2, unchecked value = 3.

declare

val number; 

begin

if(:blk_remove.chkbox_print_bill = 2)then     :blk_remove.chkbox_remove_bill := 0 ;  else         :blk_remove.chkbox_remove_bill := 1 ; end if;  exception     when others         call_note_alert('error'); 

end;

use radio buttons instead of checkboxes