Dynamically call DBMS_XMLINDEX to drop parameter and exit with exception

Hi,

I am trying to create a procedure to dynamically call DBMS_XMLINDEX.dropparameter.
If the parameter does not exist then gracefully exit with exception as 'Parameter does not exist'.
But I keep on getting errors due to dynamically passing.
Procedure is something like:

Create PROCEDURE drop_parameter(p_parameter IN VARCHAR2)
IS
no_parameter EXCEPTION;
PRAGMA EXCEPTION_INIT(no_parameter,-12004);
BEGIN
EXECUTE IMMEDIATE 'DBMS_XMLINDEX.dropparameter( ''||p_parameter||'') ';
dbms_output.put_line('Parameter dropped');
EXCEPTION
WHEN no_parameter THEN
dbms_output.put_line('Parameter does not exist');
END drop_parameter;

For implementaion we can try creating parameter as :

BEGIN
DBMS_XMLINDEX.REGISTERPARAMETER (
'Param1',
'PATH TABLE PathTB1
PATHS (INCLUDE ( /a/b/c
/d/e/f
))
');
END;
/

The above parameter should be dropped or if not existing, then exit gracefully.
Please suggest.

Thanks...