Auto-uppercase inserted column

Is there a way to automatically uppercase a column upon insert or
update?

I don't think rules can do that because of the problem of recursion. 
The only way I think it can be done is using triggers.  Is that correct?

-- 
  Bruce Momjian                        |  http://www.op.net/~candle
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026