well i'm not 100% sure if this is what you want to do, but I have a game I'm working on that flings things.
http://part12studios.com/temp/FredexTest2/
so yea if this is what you would like to be able to do... to "throw" something and have it behave with physics.. basically what you want to look at is:
apply physics impulse towards position.
impulse - (distance(Box.X,Box.Y,Touch.X,touch.Y))/10
x - touch.X
y - touch.Y
image point - 0
you'll also want to have drag/drop working as well.. though i rolled my own so I'm not sure if the drag/drop behavior would conflict with it.
good luck!
Caleb