begin
  dbms_describe.describe_procedure(object_name =>  :Object_name,
                                   reserved1 => null,
                                   reserved2 => null,
                                   overload =>  :Overload,
                                   position => :position,
                                   level => :level,
                                   argument_name => :argument_name,
                                   datatype => :datatype,
                                   default_value => :default_value,
                                   in_out => :in_out,
                                   length => :length,
                                   precision => :precision,
                                   scale => :scale,
                                   radix => :radix,
                                   spare => :spare);
end;

procedure TMyForm.DescribeButtonClick(Sender: TObject);
var Arguments: Variant;
    i: Integer;
begin
  with DescribeQuery do
  begin
    SetVariable('object_name', 'dbms_job.submit');
    Execute;
    Arguments := GetVariable('argument_name');
    for i := VarArrayLowBound(Arguments, 1) to VarArrayHighBound(Arguments, 1) do
      ShowMessage(Arguments[i]);
  end;
end;