function refreshRefNums(sheetName,refColumnIndex,refFirstRowIndex){
  var spreadSheet = SpreadsheetApp.getActive();
  var sheet = spreadSheet.getSheetByName(sheetName);
  var refLastRowIndex = sheet.getLastRow();
  var baseRange = sheet.getRange(refFirstRowIndex,refColumnIndex,2);
  var destinationRange = sheet.getRange(refFirstRowIndex,refColumnIndex,refLastRowIndex);
    baseRange.autoFill(destinationRange, SpreadsheetApp.AutoFillSeries.DEFAULT_SERIES);
}

function refreshRefNumsIOUData(){
  refreshRefNums("IOU Data",1,2);
}