Record Lock details

Hi all,

I am using PostgreSQL 7.3.1.

Is there a data dictionary in Postgres from where i can get the info about
locked rows of any table ? If possible the value of those locked record ?

My situation is like:

I have an ODBC application working on Postgres. There are Master child
tables. I want, if a user A is editing any document ( one master and set of
child records) in front-end application, the same should not be available to
other user for editing.

I thought of using SELECT FOR UPDATE. But, in my case, i need to display the
name of application user and other details about the locked row.

From which data dictionary, i should query.

Any help would be appreciated.

Thanx

Denis