GPS: way to avoid a street?

[brichi]

Hey guys, i was using the gps yesterday and it worked great, re-routed right away when I past streets and was right on. My question is, Is there a way to tell it to avoid a street b4 you even start the drive. Right now it is telling me to take a parkway that I cannot go on but I cannot figure out how to tell the gps not to use that road other then me just driving past it and then re-routing. any ideas?