How to apply “sendAlertEmailWhenCellValueIsNotEmpty” script to multiple tabs in Google Sheets

In the script it is mentioned:

//edit the following variable to fit your needs
  var cellToWatch="DAILY!W12";
  var mailAddress="someone@gmail.com";
  var emailSubject="Spreadsheet alert:BECKMAN COULTER UNICEL DXI800 MISSING DAILY MAINTENANCE";
      var emailBody="This is an email alert from your google spreadsheet:BECKMAN COULTER UNICEL DXI800 MISSING DAILY MAINTENANCE" 
  • The variable vardefined in cellToWatch="DAILY!W12" refers to cell W12 on sheet DAILY
  • mailAddress="someone@gmail.com" mentions who the email will be sent to
  • emailSubject="Spreadsheet alert:BECKMAN .... is the Subject of the email
  • emailBody="This is an email.... is the body of the email.

Play around with these variables and see what you get.

And please start reading about scripting.