SQL & PL/SQL

I don't understand why i'm getting an error.
Here's the code:

CREATE OR REPLACE PROCEDURE add_sp
 (p_table IN VARCHAR2,
  p_col   IN VARCHAR2,
  p_type  IN VARCHAR2)
 IS
  lv_cursor INTEGER;
  lv_add    VARCHAR2(100);
BEGIN
 lv_cursor:=DBMS_SQL.OPEN_CURSOR;
 lv_add:='ALTER TABLE '||p_table||' ADD ('||p_col||' '||p_type||')';
 DBMS_SQL.PARSE(lv_cursor, lv_add, DBMS_SQL.NATIVE);
 DBMS_SQL.CLOSE_CURSOR(lv_cursor);
END;
/

Procedure created.

SQL> execute add_sp('bb_shopper','standing','varchar2');
BEGIN add_sp('bb_shopper','standing','varchar2'); END;

*
ERROR at line 1:
ORA-00906: missing left parenthesis
ORA-06512: at "SYS.DBMS_SYS_SQL", line 909
ORA-06512: at "SYS.DBMS_SQL", line 39
ORA-06512: at "SYSTEM.ADD_SP", line 11
ORA-06512: at line 1

The syntax seems correct...why is this not working?