function openwcal(kalkulacka) {
var winl = (screen.width - 900) / 2 + 250;
var wint = (screen.height - 400) / 2;
winprops = 'toolbar=0, location=0, scrollbars=1, copyhistory=yes, resizable=1, height=450, width=600, top='+wint+',left='+winl;
window.open(kalkulacka, "cal", winprops);
}