Generate subtitles file in Drive from current (Excel) spreadsheet, formatted like https://docs.google.com/spreadsheets/d/1nzDgRlGuB6SY2cvfsJLH7u3_G0Ouucm-l8xsCzmfukw/edit?usp=sharing

Generate SRT.gs

function SRTstamp(_time) {
  if (_time !== undefined)
  {
    if (_time.lastIndexOf(":") < 4)
      _time = "00:"+_time
    _time = _time.replace(".",",")+"0"
    return _time
  }
  else throw("Invalid argument")
}

function genSubs() {
  var final = ""
  var capnum = 0
  var subs = SpreadsheetApp.getActiveSheet();
  cont = subs.getDataRange().getValues();
  cont.forEach(function (row) {
    if (capnum > 0)
      final += capnum.toString()+"\n"+(SRTstamp(row[0])+" --> "+SRTstamp(row[1]))+"\n"+row[2]+"\n\n";
    capnum++;
  });
  final += "\n"
  var newF = DriveApp.createFile("Captiongen"+Date.now()+"_"+subs.getSheetName()+".srt".toString(),final);
  SpreadsheetApp.getUi().alert("File created at:\n" + newF.getUrl());
}