Formula field that assigns a value based on most recent date updated

I wanna create a field named "Last update made" where it would return a value based on the most recent date updated. I have another 3 fields (Week1 Evaluation Date, Week2 Evaluation Date, Week3 Evaluation Date) to compare from. For example, if an agent was already done inputting Week1 Evaluation and Week2 Evaluation, this means the most recent date would be
Week2 Evaluation Date. So, the field "Last update made" should return "Week2 Evaluation". Please help me with setting up the formula in the field. Should this be a Formula Text? Thank you.