Good afternoon lazor99
You need to make your posts a bit clearer. If I'm reading it right you want a formula that will automatically add up the last 7 days sales (ie., without you intervening). If so use this formula:
=SUM(IF($D$2:$D$14>(NOW()-7),$E$2:$E$14,0))
This assumes you have dates in column D and values in E.
It's also an array formula so use shift + ctrl + ener to commit.
HTH
DominicB