function autoexec()
{
    Event.observe( $('image'), 'change', changeImgPath, false);
    Event.observe( $('image2'), 'change', changeImgPath2, false);
    Event.observe( $('image3'), 'change', changeImgPath3, false);
}

function changeImgPath(e)
{
    var org_action = $('sfm-form').action;
    $('sfm-form').action = 'preview.php?name1=image&name2=preview_img';
    $('sfm-form').target = 'preview_iframe';
    $('sfm-form').submit();
    $('sfm-form').action = org_action;
    $('sfm-form').target = null;
}

function changeImgPath2(e)
{
    var org_action = $('sfm-form').action;
    $('sfm-form').action = 'preview.php?name1=image2&name2=preview_img2';
    $('sfm-form').target = 'preview_iframe';
    $('sfm-form').submit();
    $('sfm-form').action = org_action;
    $('sfm-form').target = null;
}

function changeImgPath3(e)
{
    var org_action = $('sfm-form').action;
    $('sfm-form').action = 'preview.php?name1=image3&name2=preview_img3';
    $('sfm-form').target = 'preview_iframe';
    $('sfm-form').submit();
    $('sfm-form').action = org_action;
    $('sfm-form').target = null;
}

Event.observe(window, "load", autoexec);