Trigger when two item checks do not match

[twentyninehairs]

I am attempting to create a trigger that fires when the last two string values of two different items do not match. I have the following expression in my trigger. It does not seem to work.

{Template OS Windows:dnsreq.sh[{HOST.IP}].last()}<>{Template OS Windows:system.hostname[host].last()}

These are the related questions:
1. How can I troubleshoot this? I tried to create a calculated item, but I cannot find a way to use that with strings from different items.
2. Am I missing anything in the syntax of this trigger?
3. Is there another way to accomplish comparing strings from different items?

[Raido]

Found a solution for that?