How to buy condoms with out your parents knowing?

Hi im 19 and about to be sexually active. I plan on buying condoms tomorrow at Walmart but my mom will be there. If she finds out that I am about to have sex she will flip! So how do I slip away for a second to buy some? I know what isle they are in and everything and my plan was to pretend to go to the Money Gram in Walmart to put money on my rush card (which I am going to do) but after wards sneak off to buy some and then tuck them away in my purse and meet back up with her like nothing happened. Do you think I could get away with this?? What should I do?? Please help I dont wanna tell her im having sex yet.