function checkAantal(aantal) {

			val = parseInt(aantal);

			if (isNaN(val))

				return 0;

			if (val <= 0)

				return 0;

			return val;

		}

		function validate() {

			with (document.myform) {

				if (refDag.selectedIndex == 0)

				{

					alert("Please select a Day");

					return false;

				}

				if (refMaand.selectedIndex == 0)

				{

					alert("Please select a Month");

					return false;

				}

				if (refJaar.selectedIndex == 0)

				{

					alert("Please select a Year");

					return false;

				}

				if (duration.selectedIndex == 0)

				{

					alert("Please select number of days for your period");

					return false;

				}

				days = checkAantal(cyclus.value);

				if ((days <= 10) || (days >= 80))

				{

					alert("Please select a cyclus (11 - 80 days)");

					return false;

				}

			}

			return true;

		}

		function mySubmit() {

			if (validate()) document.myform.submit();

		}