var delay;
function scroll_iframe( iframe, pixel )
{
    if ( delay ) clearTimeout( delay );
    window.frames[iframe].scrollBy( 0, pixel );
    delay = setTimeout( 'scroll_iframe(\'' + iframe + '\', \'' + pixel + '\')', 5 );
} 

function stop_scroll_iframe( iframe )
{
    if ( delay ) clearTimeout( delay );
}