function CheckDivisibility(field, divno) {
	// function validates field and verifies value is divisible evening by divno passed with no reminder
	// field - field object, divno - integer e.g. 10 for field divisible by 10
	if (field.value=='') {
		// no value passed, validation failed
		return false;
	}
	var tmpField = parseInt(field.value);
	var checkdigit = tmpField % divno;
	if (checkdigit !=0) {
		// remainder exists, validation not passed
		return false;
	}
	// passed validation checks
	return true;
}