One solution is to move the ball in smaller iterations, multiple times in a given frame.
For example, and I am giving this solution assuming that you are moving the ball based on the time elapsed from the last frame.
Suppose that 30 milliseconds have elapsed since the last frame update. In that case you would update the movement/collision twice in that frame using 15 millisecond as your time elapsed.
The higher resolution of collision you want, the more iterations you would do.
Here's an example :
// class declarations
var lastFrame:Number;
var iterationsPerFrame:int;
function startGame():void
{
// lets specify 3 updates per frame
iterationsPerFrame = 3;
// save initial time
lastFrame = getTimer();
// create your listener
addEventListener(Event.ENTER_FRAME, update);
}
function update(e:Event):void
{
var currentFrame:Number = getTimer();
var deltaTime:Number = (currentFrame - lastFrame)/1000;
var iterationDelta:Number = deltaTime/iterationsPerFrame;
for (var index:int = 0;index < iterationsPerFrame;index++)
{
// I'm assuming dx,dy are the velocity of the ball, in pixels per second
ball.x += dx * iterationDelta;
ball.y += dy * iterationDelta;
// check collision
}
// set lastFrame to the currentFrame time, preparing for next frame
lastFrame = currentFrame;
// after this, your frame is going to render
}