u dont need to animate it at all.. you can just alter its scale and alpha parameters, like:

while(my.alpha>0)
{
my.scale_x+=2*time_step; //increase scale
my.scale_y=my.scale_x;
my.aplha-=30*time_step; //fade out
wait(1);
}

ofcourse you'll need a sprite with an alpha channel..

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