How to add a parameter to pass current time and export to the xml file

Hi

We have a requirement to display run time  in the report.

I tied following.

1. create parameter from concurrent program window

   token:p_run_time

value set:FND_STANDARD_DATE

current time

2.  add below formula in rdf

  v_run_date varchar2(200);

begin

  v_run_date := trunc(apps.fnd_date.canonical_to_date(:P_run_time)) ;

  return v_run_date;

  exception

when others then

v_run_date := NULL;

return v_run_date;

end;

3. compiled without error in report builder.

4.   got error when submit the program

  The error message is

REP 1247  There exist uncompiled program units .

5. the program run normally when removed the formula.