function sendEmails() {
  var sheet = SpreadsheetApp.getActiveSheet();
  var startRow = 1; // First row of data to process
  var numRows = 1; // Number of rows to process
  // Fetch the range of cells A2:B3
  var dataRange = sheet.getRange(1, 1, sheet.getLastRow(), 1);
  // Fetch values for each row in the Range.
  var data = dataRange.getValues();
  var ui = SpreadsheetApp.getUi();
  var response1 = ui.prompt('Email', 'Input name of text file here:', ui.ButtonSet.YES_NO);
  // Process the user's response.
  if (response1.getSelectedButton() == ui.Button.YES) {
    var text_file_name = response1.getResponseText();
    var files = DriveApp.getFilesByName(text_file_name); // Get all files with name.
    while (files.hasNext()) {
      var file = files.next();
      var Id = file.getId();
      var message = DocumentApp.openById(Id).getBody().getText();
      var response2 = ui.prompt('Email', 'Input email subject here:', ui.ButtonSet.YES_NO);
      if (response2.getSelectedButton() == ui.Button.YES) {
        var subject = response2.getResponseText();
        for (i in data) {
          var row = data[i];
          var emailAddress = row[0];
          var message = message;
          var subject = subject;
          MailApp.sendEmail(emailAddress, subject, message);
        }
      }
    }
  } else if (response.getSelectedButton() == ui.Button.NO) {
    Logger.log('The user didn\'t want to provide a name.');
  } else {
    Logger.log('The user clicked the close button in the dialog\'s title bar.');
  }
}