Update field in a SharePoint list based on Customer Voice submission

Hello!

I have developed a customer voice form that is currently being done by 90 people on a 2 or 3 day rotation. I have workflow to send out emails to form submitter and their managers when completed.

What I want to be able to do is send out reminders on the day they are to complete it, but only if they have NOT yet submitted a voice result.

In theory I think I know what needs to be done but I cannot find the right flow Operators.

I am thinking I would have a SharePoint list with the persons name and a field that to track update if they've completed the form. If the field is NULL meaning they havent submitted send an email reminder. If they have submitted somehow update that field to contain data to stop the reminder notification.

Any help or guidance would be greatly appreciated!