Problem with forms_ddl - capture the parameter

[alexdbora]

Hi

I have used the following when-button-pressed trigger in a form

DECLARE
procname char(10);
par1 varchar2(100);
BEGIN
procname:=:block1.name_proc;
par1:=:block1.acord;
forms_ddl('declare rezultat varchar2(200);'||'begin '||procname||'('||''''||par1||''''||',rezultat'||')'||';'||'end;');
:block1.prel_value:=rezultat;
END;
----
<procname> is a name of a procedure, which I get it from :block1.name_proc

I try to capture the out parameter named <rezultat> in a field of form :block1.prel_value , but I can't do that!
How can i display the value of rezultat in :block1.prel_value field of form?