function checkAmount() {
   var amountFilter = new RegExp("^[0-9]*$");
   var rightAmountFilter = amountFilter.exec(document.getElementById('amountEur').value);
   
   if (rightAmountFilter && (rightAmountFilter > 0)) {
      document.getElementById('amount').value=(document.getElementById('amountEur').value*100);
      document.getElementById('itemPrice1').value=document.getElementById('amount').value;
      return true;
   } else {
      alert ('Bedrag invullen, afgerond op hele Euro !');
      document.getElementById('amountEur').select();
      return false;
   }
}