PLPGSQL - FUNCTION CREATION

Hi all.

I'm trying to write a function to update a TIMESTAMP column.

MY TABLE SCHEMA:

CREATE TABLE UserLog
(
UserName NCHAR(20) NOT NULL,
ModifiedTimeStamp TIMESTAMP DEFAULT CURRENT_TIMESTAMP
)

What I want to do is that when a record is updated the ModifiedTimeStamp
column is updated to the current time.

Looking through the docs - great - create a function to do this - great -
Ohh no!

MY FUNCTION:

CREATE FUNCTION NewTimeStamp () RETURNS OPAQUE AS '
BEGIN
NEW.ModifiedTimeStamp := ''now'';
RETURN NEW;
END;
' LANGUAGE 'plpgsql';

When I execute the CREATE FUNCTION statement I get the following error:

Error: Error while executing the query;
ERROR: Unrecognized language specified in a CREATE FUNCTION: 'plpgsql'.
Recognized languages are sql, C, internal, and created procedural languages.
(State:S1000, Native Code: 7)

Help!