Can you please mention to your mother that I need to speak with her this evening? "Thank you," said Bill. "Mention not, it is hard to be thanked for nothing."
When it has a subject, verb, punctuation, capitalization, a predicate, and a complete thought. A sentence is a sentence when it is handed down by a judge (or a magistrate).
This sentence is a fragment; it lacks an independent clause. If you're going to use the helper and past participle, I would not use the words "last year." I would leave it at "If you have been to...