MC: hittest, grow in size(FlashMX6)

hi.
I want to know, that how could i make a movieclip grow, if it hits another mc.
I mean, just like in games. for example, Fishy. the fish hits the smaller fish, and it grows in size.
Now, my problem is, that i’ve got absolutely no idea, that how to make a smiliar code.
Any ideas?:slight_smile: