Sum values from a certain date onwards

Hi All


I have sales by day for a month. I have identified when a promo order was sold to an account. I need to be able to calculate the total sales for the rest of the month after the promo was sold. Please see attached file.

Since I have the date, I was thinking maybe i can do a Hlook to get a value but then get the cell address of that value and then do a sum till till the address of the cell in the last column but i am not sure how to go about doing it.

Any help is greatly appreciated. Thanks