http://www.alwaystestclean.com/hair_drug_test.htm - info on how the test works and what the shampoo's do.
Google some more info. There's a good possibility the shampoo's may work. If they don't, well... it was worth a try. There's also a good posibility that the test won't pick anything up (depending on how often you smoke). These shampoo's are for people that smoke 1-2 times a week, not once a month [assumed].