In Plankexercise: Can you get a toned belly by sucking it in during the day

Can you get a toned belly by sucking it in during the day? I have always pretty much let my belly hang loose during my day to day. I know this is a bad habit, but I've never had a big belly, but now that I'm a breastfeeding momma, I'm trying to build back my abdominal muscles. I love the pilates DVD I have () and ...Plankexercise