so to get this right :

three balls

You roll over the first ball and it increases and the second and third decrease
You roll Out and all return to the normal size:

if so this is easy enough with a little twick I beleive, what your after originally is :
When you mouse over bubble 1, it increases in size, bubbles 2 and 3 become smaller. You then mouse over directly to bubble 2, which increases to a bigger size (not normal size), bubble 1 reduces, bubble 3 gets bigger and smaller again!
you need to move mouse quickly but as soon as you move the mouse to rollOut mode it would initiate that function so your nearly as close as you could get with the code etc