function isNotNull(feld) {
	if(document.getElementsByName(feld)[0].value == ''){
		document.getElementsByName(feld)[0].value = 1;
	}
}

function onlyNum(feld){
	if(isNaN(document.getElementsByName(feld)[0].value) == true)
	{	
		document.getElementsByName(feld)[0].value = document.getElementsByName(feld)[0].value.substring(0,document.getElementsByName(feld)[0].value.length-1);
	}
}