function markprod () {
	var numchecks = 0;

	if (document.getElementById("prod1") != null) { if (document.getElementById("prod1").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod2") != null) { if (document.getElementById("prod2").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod3") != null) { if (document.getElementById("prod3").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod4") != null) { if (document.getElementById("prod4").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod5") != null) { if (document.getElementById("prod5").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod6") != null) { if (document.getElementById("prod6").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod7") != null) { if (document.getElementById("prod7").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod8") != null) { if (document.getElementById("prod8").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod9") != null) { if (document.getElementById("prod9").checked == true) { numchecks = numchecks + 1; } }
	if (document.getElementById("prod10") != null) { if (document.getElementById("prod10").checked == true) { numchecks = numchecks + 1; } }

	if (numchecks == 2) {
		if (document.getElementById("prod1") != null) { if (document.getElementById("prod1").checked == false) document.getElementById("prod1").disabled = true; }
		if (document.getElementById("prod2") != null) { if (document.getElementById("prod2").checked == false) document.getElementById("prod2").disabled = true; }
		if (document.getElementById("prod3") != null) { if (document.getElementById("prod3").checked == false) document.getElementById("prod3").disabled = true; }
		if (document.getElementById("prod4") != null) { if (document.getElementById("prod4").checked == false) document.getElementById("prod4").disabled = true; }
		if (document.getElementById("prod5") != null) { if (document.getElementById("prod5").checked == false) document.getElementById("prod5").disabled = true; }
		if (document.getElementById("prod6") != null) { if (document.getElementById("prod6").checked == false) document.getElementById("prod6").disabled = true; }
		if (document.getElementById("prod7") != null) { if (document.getElementById("prod7").checked == false) document.getElementById("prod7").disabled = true; }
		if (document.getElementById("prod8") != null) { if (document.getElementById("prod8").checked == false) document.getElementById("prod8").disabled = true; }
		if (document.getElementById("prod9") != null) { if (document.getElementById("prod9").checked == false) document.getElementById("prod9").disabled = true; }
		if (document.getElementById("prod10") != null) { if (document.getElementById("prod10").checked == false) document.getElementById("prod10").disabled = true; }
	}
	else {
		if (document.getElementById("prod1") != null) {document.getElementById("prod1").disabled = false; }
		if (document.getElementById("prod2") != null) {document.getElementById("prod2").disabled = false; }
		if (document.getElementById("prod3") != null) {document.getElementById("prod3").disabled = false; }
		if (document.getElementById("prod4") != null) {document.getElementById("prod4").disabled = false; }
		if (document.getElementById("prod5") != null) {document.getElementById("prod5").disabled = false; }
		if (document.getElementById("prod6") != null) {document.getElementById("prod6").disabled = false; }
		if (document.getElementById("prod7") != null) {document.getElementById("prod7").disabled = false; }
		if (document.getElementById("prod8") != null) {document.getElementById("prod8").disabled = false; }
		if (document.getElementById("prod9") != null) {document.getElementById("prod9").disabled = false; }
		if (document.getElementById("prod10") != null) {document.getElementById("prod10").disabled = false; }
	}
}