With(mc){...} doesn't passing variables?

1

In the flash help the following works
on(release) {
with(_root.ball) {
gotoAndPlay(2);
_alpha = 15;
_xscale = 50;
_yscale = 50;
}
}

but when I add myVar = 10 it doesn’t go into the _root.ball but the _root only.
Is there a way to add lots of variables to a mc without having to type mc.var1=…, mc.var2=…etc.
Thanks in advanced!
-Miro