A question regarding double opt in

If someone is already on my list, and they fill in another one of my sign up forms (in my current case to sign up to a special event), they get the double opt in email again, asking them to confirm (plus the event-related automated welcome email at the same time). Can I stop this just for the people already on my list? I want to keep the double opt in as I also have people signing up who are not on my list yet. For them it works perfectly- first they get the double opt in email, then the automated welcome email. I just don’t want people already on my list to get the double opt in email again. Is this possible? I’m grateful for any tips or advice