using forms/making reminders



I'm trying to use a contact list sheet to send out a reminder to fill out a form. However, if the recipient doesn't fill out the form how do I make a reminder if there's no data in the sheet that received the form info? I'm trying to avoid manual work. This will also change every week. So the contact list could change and the request to fill out the form goes out every week with a reminder on Wednesdays and Fridays.

How do I figure out who didn't fill out the form and remind them we need the data? How do I run reports on a lack of data?