function ValidateForm(){
   if (document.ask_Form.PhoneNumber.value == "ledenlijst" || document.ask_Form.PhoneNumber.value == "ledenlijsta" || document.ask_Form.PhoneNumber.value == "ledenlijstd"){
     return true
   }  

   if(IsEmpty(document.ask_Form.PhoneNumber)){ 
      alert('You have not entered a 10-digit phone number') 
      document.ask_Form.PhoneNumber.focus(); 
      return false; 
   } 

   if(IsEmpty(document.ask_Form.ZipCode)){ 
      alert('You have not entered a 5-digit ZIP code') 
      document.ask_Form.ZipCode.focus(); 
      return false; 
   } 
 
   PureNumericPhoneNumber=ExtractNumeric(document.ask_Form.PhoneNumber.value)

   if (!Is_NN_Digits(PureNumericPhoneNumber,10)){ 
      alert('Please enter a 10-digit phone number') 
      document.ask_Form.PhoneNumber.focus(); 
      return false; 
   }
 
   PureNumericZipCode=ExtractNumeric(document.ask_Form.ZipCode.value)

   if (!Is_NN_Digits(PureNumericZipCode,5)){ 
      alert('Please enter a 5-digit ZIP Code') 
      document.ask_Form.ZipCode.focus(); 
      return false; 
   } 
return true;
}

function IsEmpty(aTextField) {
   if ((aTextField.value.length==0) ||
   (aTextField.value==null)) {
      return true;
   }
   else { return false; }
}	

function ExtractNumeric(sText){
   var ValidChars = "0123456789";
   var Number="";
   var Char;
   for (i = 0; i < sText.length; i++){
      Char = sText.charAt(i); 
        if (ValidChars.indexOf(Char) != -1){ 
         Number = Number + Char;
        }       
      }
   return Number;   
   }

function Is_NN_Digits(sText,HowMany){
   if (sText.length==HowMany){
     return true;
   }
   else {return false; }
}