function ValidateRequiredFields(formId, RequiredFields)
{
	var FieldList = RequiredFields.split(",");
	var BadList = new Array();
	for (var i = 0; i < FieldList.length; i++)
	{
		if (FieldList[i] == 'postcode')
		{
			var value = document.getElementById(formId).postcode.value;
			if (isNaN(value.substr(0, 4)))
			{
				BadList.push('Postcode is in het verkeerde formaat. (1234)'); 
			}
		}
		var s = eval('document.getElementById(\'' + formId + '\').' + FieldList[i] + '.value');

		if(s.length < 1)
		{ 
			BadList.push(FieldList[i]); 
		}
	}

	if(BadList.length < 1)
	{ 
		return true;
	}

	var message = new String('De volgende velden zijn verplicht:');
	for(var i = 0; i < BadList.length; i++)
	{ 
		message += '\n- ' + value2name(BadList[i]); 
	}

	alert (message);
	return false;
}

function value2name(value)
{
	value = value.replace("_sl_", " / ");
	value = value.replace("_st_", "-");
	value = value.replace("_", " ");
	value = ucfirst(value);
	

	return value;
}

function ucfirst(str)
{ 
	var f = str.charAt(0).toUpperCase();
	return f + str.substr(1, str.length-1);
}