How to prevent a timestamp from being edited

Question

I have been trying to edit the following code so that every time columnname cantidad is edited i get a timestamp con columnname solicitado, the problem i am having and would like help with is preventing that timestamp from being edited by anyone.

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function onEdit(event) 
{ 
  var timezone = "GMT-04:00";
  var timezone2 = "GMT-04:00";
  var timezone3 = "GMT-04:00";
  var timestamp_format = "MM-dd-yyyy hh:mm:ss"; // Timestamp 12hour Format
  var timestamp_format2 =  "MM-dd-yyyy hh:mm:ss"; // Timestamp 12hour Format
  var timestamp_format3 =  "MM-dd-yyyy hh:mm:ss"; // Timestamp 12hour Format
  var updateColName = "CANTIDAD"; var timeStampColName = "SOLICITADO";
  var updateColName2 = "CANTIDAD ORDENADO"; var timeStampColName2 = "FECHA ORDENADO"
  var updateColName3 = "CANTIDAD ENTREGADA"; var timeStampColName3 = "FECHA DE ENTREGA"
  var sheet = event.source.getSheetByName('Sheet1'); //Name of the sheet where you want to run this script. 


  var actRng = event.source.getActiveRange(); 
  var editColumn = actRng.getColumn(); 
  var index = actRng.getRowIndex(); 
  var headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues(); 
  var dateCol = headers[0].indexOf(timeStampColName); 
  var updateCol = headers[0].indexOf(updateColName); updateCol = updateCol+1; 
  if (dateCol > -1 && index > 1 && editColumn == updateCol) { // only timestamp if 'Last Updated' header exists, but not in the header row itself! 
   var cell = sheet.getRange(index, dateCol + 1); 
   var date = Utilities.formatDate(new Date(), timezone, timestamp_format); 
   cell.setValue(date); 
  } 

  var actRng = event.source.getActiveRange(); 
  var editColumn = actRng.getColumn(); 
  var index = actRng.getRowIndex(); 
  var headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues(); 
  var dateCol = headers[0].indexOf(timeStampColName2); 
  var updateCol = headers[0].indexOf(updateColName2); updateCol = updateCol+1; 
  if (dateCol > -1 && index > 1 && editColumn == updateCol) { // only timestamp if 'Last Updated' header exists, but not in the header row itself! 
   var cell = sheet.getRange(index, dateCol + 1); 
   var date = Utilities.formatDate(new Date(), timezone2, timestamp_format2); 
   cell.setValue(date); 

}
    var actRng = event.source.getActiveRange(); 
  var editColumn = actRng.getColumn(); 
  var index = actRng.getRowIndex(); 
  var headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues(); 
  var dateCol = headers[0].indexOf(timeStampColName3); 
  var updateCol = headers[0].indexOf(updateColName3); updateCol = updateCol+1; 
  if (dateCol > -1 && index > 1 && editColumn == updateCol) { // only timestamp if 'Last Updated' header exists, but not in the header row itself! 
   var cell = sheet.getRange(index, dateCol + 1); 
   var date = Utilities.formatDate(new Date(), timezone3, timestamp_format3); 
   cell.setValue(date);

}

}