I would like to apply this to let's say "Weekly" and "Monthly" tab. Here's my script:
function sendAlertEmailWhenCellValueIsNotEmpty(){
//send an email alert when cellToWatch is not empty
//set this function to run through a time driven trigger
//choose resource> Current project's triggers> Add a new trigger>Time-driven>Day Timer
//see https://productforums.google/d/topic/docs/39Ysmg7nAjk/discussion
//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"
if(SpreadsheetApp.getActiveSpreadsheet().getRange(cellToWatch).getValue()!=""){
MailApp.sendEmail(emailAddress,emailSubject,emailBody);
}
}