owa_util.listprint

Are there any code samples to get this function to work?

This is the error message that I get:

OWS-05101: Execution failed due to Oracle error 904
ORA-00904: invalid column name
ORA-06512: at "SYS.DBMS_SYS_SQL", line 239
ORA-06512: at "SYS.DBMS_SQL", line 32
ORA-06512: at "WAIMEI.OWA_UTIL", line 1420
ORA-06512: at "WAIMEI.OWA_UTIL", line 1568
ORA-06512: at "WAIMEI.SV_CAL", line 24
ORA-06512: at line 1

My code is below:

 owa_util.listprint('select maintain.site_id a, site.name b, ''null'' n

                            from maintain, site
                            where maintain.site_id = site.site_id
                              and maintain.user_id = ' || urec.user_id,
      'yh', 1, TRUE);