Relative Dates Formula

I am creating a simple activity tracker for my salespeople to log business development KPIs. The idea is that they would fill out a form to summarize business generation activities from the previous week. Iā€™m trying to have Noloco automatically input the date for the Sunday from the previous week. Is it possible to add a formula to the relative date field so that if I select End of Week it would subtract 7 days to input the Sunday from the previous week instead of the Saturday from the current week?