sheets_slack_notification.gs

function buildReport() {
  const ss = SpreadsheetApp.getActive();
  const data = ss.getSheetByName('SUMMARY').getRange("A1").getValues();
  const payload = buildAlert(data);
  Logger.log(data);
  sendAlert(payload);
}

function buildAlert(data) {
  const mrr = data[0][0];

  const payload = {
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": ":bell: *Daily MRR Report* :bell:"
        }
      },
      {
        "type": "divider"
      },
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "Our NET MRR for this month is " + mrr
        }
      }
    ]
  };

  return payload;
}

function sendAlert(payload) {
  const webhook = "https://hooks.slack.com/services/<your-webhook-goes-here>";
  const options = {
    "method": "post", 
    "contentType": "application/json", 
    "muteHttpExceptions": true, 
    "payload": JSON.stringify(payload) 
  };
  
  try {
    UrlFetchApp.fetch(webhook, options);
  } catch(e) {
    Logger.log(e);
  }
}