parameter problem..

I am new to developer6 form builder.so its a totally newbie question..
I have 2 forms , form1 and form2.I am creating a control block in form 1 and display a combobox in which I populate the list with department numbers from dept table by when_new_form_instance trigger as

DECLARE
l_deptno number;
indx number;
cursor cur_dept
is
select deptno
from dept
order by
deptno desc;

BEGIN
Set_Window_Property(FORMS_MDI_WINDOW, WINDOW_STATE, MAXIMIZE);
Set_Window_Property('window1', WINDOW_STATE, MAXIMIZE);

indx:= 1;

OPEN cur_dept;

LOOP
fetch cur_dept into l_deptno;
if cur_dept%NOTFOUND
then
exit;
end if;

Add_List_Element('control.deptno',indx,l_deptno,l_deptno);

indx:=indx + 1;

END LOOP;
CLOSE Cur_dept;
END;

I have got a parameter as deptno in form1 and a button in form1.Upon clicking button , I want to pass this parameter to form2.

declare
list_id ParamList;
begin
list_id := create_parameter_list('passing_params');
add_parameter(list_id,'deptno', TEXT_PARAMETER, :control.deptno);

call_form('form2', NO_HIDE, NO_REPLACE, NO_QUERY_ONLY, 'passing_params');

destroy_parameter_list('passing_params');
end if;
end;

but I am not able to access this parameter in form2.Created a similar parameter deptno in form2.When I try to set access it , it says no such parameter deptno in form2. I have checked its existance and also the datatypes.

What can be the error?
Please help,
Thanks