function checkfields()
	{
	if (document.getElementById("commercial_class").value=="")
		{
		document.getElementById("check_com_1").value="6"
		document.getElementById("check_com_2").value="7"
		document.getElementById("check_com_3").value="8";
		}
	if (document.getElementById("commercial_class").value!=="")
		{
		document.getElementById("check_com_1").value=""
		document.getElementById("check_com_2").value=""
		document.getElementById("check_com_3").value="";
		}
	if (document.getElementById("pclassland").value=="")
		{
		document.getElementById("check_land_1").value="18"
		document.getElementById("check_land_2").value="19"
		document.getElementById("check_land_3").value="20"
		document.getElementById("check_land_4").value="21"
		document.getElementById("check_land_4").value="22";
		}
	if (document.getElementById("pclassland").value!=="")
		{
		document.getElementById("check_land_1").value=""
		document.getElementById("check_land_2").value=""
		document.getElementById("check_land_3").value=""
		document.getElementById("check_land_4").value=""
		document.getElementById("check_land_4").value="";
		}
	if (document.getElementById("rentalclass").value=="")
		{
		document.getElementById("check_rental_1").value="8"
		document.getElementById("check_rental_2").value="14";
		}
	if (document.getElementById("rentalclass").value!=="")
		{
		document.getElementById("check_rental_1").value=""
		document.getElementById("check_rental_2").value="";
		}
	
	}