function radio_button_checker()
{
// set var radio_choice to false
var radio_choice = false;
var elements = document.getElementsByTagName('radio');

// Loop from zero to the one minus the number of radio button selections
for (var i=0; i<radio_form.elements.length; i++)
	{
	// If a radio button has been selected it will return true
	// (If not it will return false)
	if (radio_form.elements[i].checked)
	radio_choice = true; 
	}

if (!radio_choice)
	{
	// If there were no selections made display an alert box 
	alert("Maak eerst een keuze")
	return (false);
	}
return (true);
}