trigger jquery

Hi,
I’m using search autocomplete to check if a flavour is available in a database. To accomplish that, I’m using wp tags as entity (in my website I don’t need tags). So when an users search for a flavour/tag, the search autocomplete suggests it and then it should display two different messages if the tag has been found or not.
So, I’m wondering how to retrieve an event from the search field when the tag is found (even if there are no post associated) and then trigger a jquery function.

best,
Matteo