var bBSDIsSet = false;
function checkDates(sType, sName) {
    var difference = 21;
    switch (sName) {
    case 'vnd':
        if (!bBSDIsSet) {
    		if ((document.forms[sType].vnd.selectedIndex + difference) <= document.forms[sType].bsd.options.length) {
    			document.forms[sType].bsd.selectedIndex =  document.forms[sType].vnd.selectedIndex + difference;
    		} else {
    			document.forms[sType].bsd.selectedIndex = document.forms[sType].bsd.options.length - 1;
    		}
        }
    	break;
    case 'bsd':
        bBSDIsSet = true;
    	break;
    case 'mmc':
    	break;
    }
    var sErrorMessage = checkSettings(sType);
    if (sErrorMessage != '') {
        alert("Achtung, \n" + sErrorMessage);
    }
}
function checkSettings(sType) {
    var sError = '';
    var sDuration = (document.forms[sType].mmc.options[document.forms[sType].mmc.selectedIndex].value);
	switch(sDuration) {
		case "0": iDuration = 0; break;
		case "1-5t": iDuration = 5; break;
		case "1w": iDuration = 7; break;
		case "6-8t": iDuration = 8; break;
		case "9-12t": iDuration = 12; break;
		case "2w": iDuration = 14; break;
		case "13-16t": iDuration = 16; break;
		case "3w": iDuration = 21; break;
		case "17-22t": iDuration = 22; break;
		case "4w": iDuration = 28; break;
		case "27-28t": iDuration = 28; break;
		default: iDuration = 0; break;
	}

    if (document.forms[sType].bsd.selectedIndex < document.forms[sType].vnd.selectedIndex + iDuration) {
        sError += 'Die Reisedauer, die Sie eingestellt haben, ist länger als'
            + ' der Zeitraum zwischen dem An- und Abreisedatum.';
    }
    if (document.forms[sType].bsd.selectedIndex < document.forms[sType].vnd.selectedIndex) {
        sError += 'Das Rückreisedatum muss nach dem Anreisedatum liegen';
    }
    return sError;
}