Here is the Think or Swim code for multi-day VWAP - you select the start date, you can day 2 days, 50 days, a year, etc.
input startDateYyyyMmDd = 20171116;
def beyondStartDate = if GetYYYYMMDD() >= startDateYyyyMmDd then 1 else 0;
plot VWAP = TotalSum(if beyondStartDate then (((high + low +...