how to create a trigger compares two string items?

[sersad]

how to create a trigger compares two string items, to operate under the condition that they are different.
There are two string values of the two an item.
card10soft = "she-r23-iu_adsl72ifxa-o.743"
card10softupg ="she-r23-iu_adsl72ifxa-o.746"
You must write a trigger that would have worked in the case if these lines are not equal to each other.
Reading the documentation it has

({{HOSTNAME}:card10softupg.last(0)}<{{HOSTNAME}:card10soft.last(0)})
 | 
({{HOSTNAME}:card10softupg.last(0)}>{{HOSTNAME}:card10soft.last(0)})

or

{{HOSTNAME}:card10softupg.last(0)}#{{HOSTNAME}:card10soft.last(0)}

However, these triggers do not work. The status they have always known. The value of an item obtained without problems.

Any solution?

[sersad]

have any ideas?