function energyUse() {
	
	if(document.getElementById('sbm')){document.getElementById('sbm').disabled = true};
	
	var f			= document.getElementById('energieverbruik');
	var Weight		= f.Weight.value;
	var Time		= f.Time.value;
	var KcalActi	= f.KcalActi.value;
	var sError		= "";
	var strFocus	= "";
	
	if(Weight == ""){sError = sError + "- U hebt geen gewicht ingevuld\n"; if(strFocus == ""){strFocus = "Weight";}}
	if(Time == ""){sError = sError + "- U hebt geen tijd ingevuld\n"; if(strFocus == ""){strFocus = "Time";}}
	if(KcalActi == "-1"){sError = sError + "- U hebt geen activiteit gekozen\n"; if(strFocus == ""){strFocus = "KcalActi";}}
	
	if (sError != "")
	{
		alert('De volgende gegevens ontbreken of zijn onvolledig.\n\n'+sError+'');
		if(document.getElementById('sbm')){document.getElementById('sbm').disabled = false};
		if(strFocus != "")
		{
		eval("document.getElementById('"+strFocus+"').focus();");
		}
	}
	else
	{
		f.action = "./";
		f.submit();
	}
}