Flash Actionscript + detecting collision at edges

I have two circular objects. I'm trying to detect as soon as the circles touch. The trace detects a collision when one circle reaches the center of the other but I want the collis开发者_如何学运维ion to be detected as soon as the circles touch.

My two symbols are coin_mc and mugbounds_mc.

function checkHitArea(evt:Event)
{

 if (coin_mc.hitTestPoint(mugbounds_mc.x,mugbounds_mc.y, true)) {
  coin_mc.x=-1;
  coin_mc.y=-1;

                trace("Hit Mug"); // Is triggered when coin_mc reaches center of mugbounds_mc
        }
        else
        {
                trace("Didn't Hit Mug");
        }
}

Try this:

addEventListener(Event.ENTER_FRAME, checkHitArea)

function checkHitArea(e:Event) 
{
    a.x += 2;
    if (a.hitTestPoint(b.x,b.y, false)) 
    { 
        // do our in-circle check
        if((a.x - b.x) * 2 + (a.y - b.y) * 2 <= (a.width/2 + b.width/2) * 2)
        {
            trace("hit");
        }
    }
    else
    {
        trace("Didn't Hit Mug");
    }
}

I renamed your movie clips to a and b.