[Xymon] inverted http test

I am looking for a way to check if a domain is available and if, I would like to get an alert. I know, I usually can do it with an ! in the beginning of a test, but this doesn't seems to work for http tests.

Here my test:

192.168.144.254 MyDomain # NET:intern NAME:"MyDomain" !telnet !http://MyDomain.com !conn

I think that just "!http" should work.

Regards, Henrik