Tablerights for User in Group

Hi,

Is it possible to query de backend database for retrieving rights of an
user in a group for a
table?

I know that the userrights can be retrieved as:

SELECT relacl FROM pg_class WHERE relname = '[table name]'

and the users-id in groups as:

SELECT grolist from pg_group where groname = 'group'

the user-id;

SELECT usesysid from pg_user where usename = 'name';

How can I query

SELECT rights FROM table WHERE usename = 'name' AND relname = '[tablename]' ....

Otherwise I have to query the backend and parse and parse and parse .... the results.

TIA

WIllem.