mSprites.SortYInsertion();

if(ball.YVelocity < 0)
{
    // Ball is moving down, so forward loop to 
    // check top to bottom.
    for( int i = 0; i < mSprites.Count; i++)
    {
         PreformSpriteCollision(mSprites[i]);

         if (!start)
              break;
    }
}
else
{
    // Ball is moving up, so reverse loop to
    // check bottom to top.
    for( int i = mSprites.Count - 1; i > - 1; i--)
    {
         PreformSpriteCollision(mSprites[i]);

         if (!start)
              break;
    }
}