Variable with variable name

Hi I’m wondering how do u call a variable that has a variable name.

max = 10;

For (i=1; i<=max; i++)
this.attachMovie(“expBall”, “ball”+i, i);


Now I want
ball1._x = 100i;
ball2._x = 100

until ball10._x=100*i;

how can i do that? how do i address a variable name which is variable?