What drives this sentence to be in the subjunctive tense?

Bonjour Donald, I looked at the lesson referenced above and was unable to locate the sentence you mentioned. Is there a specific phrase that you had in mind? I too am curious at times when I read a phrase in French to know what drives the verb tense other than the French grammar rules. I am quite intrigued with your question and look forward to a knowledgeable reply from the Kwiziq team. There must be some underlying rationale, other than just the rules, as to the reasons the subjunctive is used. Bonne chance, Ron

Je suis désolé. En ce moment, je ne peux pas le trouver. Quand je le trouverai, je vous l'enverrai. Merci d'avoir essayé m'aider. Je ne veux pas vous gaspiller votre temps. Peut-être c'est une autre question- ca veut-dire, l'usage de au lieu d'un autre verbe.