function checkPhonenumber( form ){
phonenumber = form.phonenumber.value;
phonenumber.replace(/-| /g,'');

if (phonenumber == "") {
document.getElementById('messageArea').innerHTML = "Geen telefoonnummer ingevuld";
form.phonenumber.focus();
return false ;
} else if (phonenumber.length < 8 || phonenumber.length > 12) {
document.getElementById('messageArea').innerHTML = "Ongeldig telefoonnummer ingevuld";
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 ingevuld";
form.phonenumber.focus();
return false ;
} else {
document.getElementById('messageArea').innerHTML = "";
window.open('', 'foo', 'width=460, height=360,status=no,resizable=no,scrollbars=no');
return true ;
}
}