RULE Problem with pseudo relations OLD/NEW

I use Postgresql 7.2.1 on Debian Linux
3.0r1. 
I have tried to create a RULE exactly as described in the "Postgresql
Programmers Manual". Code: 

CREATE RULE foo_rule AS ON UPDATE TO foo WHERE  NEW.footxt  !=
OLD.footxt 
       DO UPDATE gaga SET NEW.foodate = CURRENT_TIMESTAMP;

Then I receive the error message: 

ERROR:  parser: parse error at or near "NEW"

I tried different ways, but it never created the rule. One time it gave
me the error message, that the relation *NEW* doesn't exist...
What's wrong? How can I work with the pseudo relations NEW or OLD, so that
postgresql accepts it? 

Thanks in advance for any help!

Kurt Gerber