Attempting to create a Weekly Time Sheet system where users have to create Daily Time Card records. If there is a Daily Time Card detail record already created for that day on the Weekly TIme Sheet master record, is there a way to use a validation rule or perhaps a beforeinsert trigger to prevent a duplicate record from being created on the same day by that user? 

Attempting to create a Weekly Time Sheet system where users have to create Daily Time Card records. If there is a Daily Time Card detail record already created for that day on the Weekly TIme Sheet master record, is there a way to use a validation rule or perhaps a beforeinsert trigger to prevent a duplicate record from being created on the same day by that user?