var theWindow=0;
function openWindow(theURL,theWidth,theHeight,theProps) {
	theWidth = (theWidth) ? theWidth : 260
	theHeight = (theHeight) ? theHeight : 250
	theProps = (theProps) ? (theProps+',') : ''
	if (theWindow==0) {
		// nog niet eerder een venster geopend
		theWindow = window.open(theURL,'nieuwWindow',theProps+'resizable=yes,width='+theWidth+',height='+theHeight);
		theWindow.focus();
	} else {
		if (theWindow.closed) {
			// window al gesloten
			theWindow = window.open(theURL,'nieuwWindow',theProps+'resizable=yes,width='+theWidth+',height='+theHeight);
			theWindow.focus();
		} else {
			// window nog steeds open
			theWindow.location.href = theURL;
			theWindow.focus();
		}
	}
}