var fenst = 0;
                var istschon = 0;
                var jm = 0;

function fenster(jm) {
if (istschon == 0){
fenst= window.open(jm,'neufenst','resizable=0,scrollbars=yes,toolbar=no,width=800,height=700');
istschon = 1}
else
{nachvorne(jm);}
}

function nachvorne(jm) {
if (fenst.closed){
fenst= window.open(jm,'neufenst','resizable=0,scrollbars=yes,toolbar=no,width=800,height=700');
}
else
{
fenst.focus();
fenst= window.open(jm,'neufenst','resizable=0,scrollbars=yes,toolbar=no,width=800,height=700');
}}