// Handling forms

// true if one or more checkboxes are checked in aForm, false otherwise
function checkboxChecked( aForm ) {
	var bOK = false;
	var aInputs = document.forms[aForm].getElementsByTagName("input");

	for (var x=0; x<aInputs.length; x++) {
		if (aInputs[x].type == "checkbox") {
			if ( aInputs[x].checked == true ) { 
				bOK = true;
				break;
			}
		}
	}

	if ( !bOK ) { alert( "Klik eerst op een of meer keuzevakjes." ) }

	return bOK;
}