Is there a alcohol test that can detect back 7 days?

There are blood tests that can detect alcohol use that occurred even longer than 7 days. Usually only larger amounts or prolonged drinking however. These tests are not detecting alcohol (ethanol) rather physiological changes that result from drinking.

Phosphatidylethanol (PeTH) is an example, detectable at 2 weeks post-consumption. There are several others as well. (Ex. See Hartmann, et al, 2007 (http://www.citeulike.org/user/softsimu/article/2280801))

These Tests Do Not Detect Alsohol, But The Metabolites Left Over From The Metabolism Of Alcohol By The Liver. 7 Days? Yes They Can, Sometimes Longer Than 7 Days. Don't Rish It. If You Are On Parole Or Probation, Obey The Rules, Then When You Time Is Up, Drink If You Want To. But Don''t Drive At The Same Time!