Tags are assigned based on the document class, so unless you want to (a) apply different document classes based on which word was found or (b) use Quick Fields scripting, you won't be able to do this using Quick Fields only.

However, it can be accomplished with a tiny bit of Workflow. I would recommend using Quick Fields to capture and store the relevant information to a field (it can be a hidden field if you wish) and then using Workflow to read the field value and assign the tag accordingly.