/***********************************************
* Validate Data Entered
***********************************************/

 function IsEmptyOrInteger(strString)
 //  check for valid numeric strings	
 {
   if (strString.length == 0)
   {
     // alert('String is empty');
     return true;
   }

   var strValidChars = "0123456789";
   var strChar;
   var blnResult = true;

   //  test strString consists of valid characters listed above
   for (i = 0; i < strString.length && blnResult == true; i++)
   {
     strChar = strString.charAt(i);
     if (strValidChars.indexOf(strChar) == -1)
     {
       alert('Alleen cijfers ingeven a.u.b.\n\nWaarde "' + strString + '" bevat niet alleen cijfers,\nde ' + strChar + ' op positie ' + eval(i+1) + ' is fout.');
       blnResult = false;
     }
   }
   return blnResult;
 }