If you want to get the previous Friday from today
=TODAY()-WEEKDAY(TODAY()+1)
so the following Thursday from that would be just that value plus 6 so you can either use
=TODAY()-WEEKDAY(TODAY()+1)+6
or reference the cell with the first formula and add 6...With those formulas today you'll get 1st Jan to 7th Jan but tomorrow that will change to 8th to 14th and remain like that for a week, is that what you need?
regards, barry