function checkFormInput(form) {

	// check the mandatory fields
	var missingFields = "";
	var validInput = true;
	for (var i = 0; i < form.elements.length; i++) {
		var elementName = form.elements[i].name;
		if (elementName == 'mandatoryField') {
			var elementValue = form.elements[i].value;
			var mandatoryElement = form.elements[elementValue];
			if (mandatoryElement.value.length === 0) {
				validInput = false;
				var startPosition = mandatoryElement.name.indexOf('_', 9);
				var displayName = mandatoryElement.name.substr(startPosition + 1);
				missingFields += "\n\t" + displayName;
			}
		}
	}

	if (validInput) {
		form.submit();
	} else {

		// find the error message
		var errorMessage = "The following fields are empty:";
		var foundMessage = false;
		var index = 0;
		while (!foundMessage && index < form.elements.length) {
			if (form.elements[index].name == 'errorMessage') {
				errorMessage = form.elements[index].value;
				foundMessage = true;
			} else {
				index++;
			}
		}

		// show the error message
		alert(errorMessage + missingFields);
	}
}