function checkPhonenumber( form ){
	phonenumber = form.phonenumber.value;
	phonenumber.replace(/-| /g,'');
	
	if (phonenumber == "") {
	document.getElementById('messageArea').innerHTML = "Telefoonnummer invullen";
	form.phonenumber.focus();
	return false ;
	} else if (phonenumber.length < 8 || phonenumber.length > 12) {
	document.getElementById('messageArea').innerHTML = "Ongeldig telefoonnummer";
	form.phonenumber.focus();
	return false ;
	} else if (phonenumber.charAt(1) == 8){
	document.getElementById('messageArea').innerHTML = "Geen servicenummers toegestaan";
	form.phonenumber.focus();
	return false ;
	} else if (phonenumber.charAt(1) == 9){
	if (phonenumber.substring(2,4) == 91){
	return true;
	} else {
	document.getElementById('messageArea').innerHTML = "Geen servicenummers toegestaan";
	form.phonenumber.focus();
	return false ;
	}
	} else if (phonenumber.charAt(0) != '+' && phonenumber.charAt(0) != 0){
	document.getElementById('messageArea').innerHTML = "Ongeldig telefoonnummer";
	form.phonenumber.focus();
	return false ;
	} else {
	document.getElementById('messageArea').innerHTML = "";
	window.open('', 'foo', 'width=460, height=260,status=no,resizable=no,scrollbars=no');
	return true ;
	}
}