var mvUp = false;
var mvDown = true;

var ballStep = 10;

function ballExec()
{   
    oCont = document.getElementById( 'CUR0' );
    oBall = document.getElementById( 'ball' );
    oBall.style.display = '';
    if( IS_REPLACE ) return;
    ballDY = parseInt(oBall.style.top) - parseInt(oCont.style.top);
    
    if( mvDown )
    {
        if( ballDY < clHeight - 40 )
        {              
            oBall.style.top = parseInt(oBall.style.top) + ballStep; 
        }
        else
        {
            mvUp = true;
            mvDown = false;
        }
    }
    else
    {
        if( ballDY > 5 )
        {
            oBall.style.top = parseInt(oBall.style.top) - ballStep; 
        }
        else
        {
            mvUp = false;
            mvDown = true;
        }
    }   
}