How to run a Google Apps Script on a hidden sheet

I have a sheet that is hidden that determines who will be emailed. The script that I have now will not run without having the sheet opened. Is it possible to run that GAS without having to unhide the hidden sheet?

function sendEmails() {
   var sheet = SpreadsheetApp.getActiveSheet();

   var range = sheet.getRange(1,3);   
   var email = range.getValues();     
   var emailAddress = email[0][0];    

   var range = sheet.getRange(2,3);   // Fetch the range of cells E1:E1
   var CC = range.getValues();        
   var ccEmail = CC[0][0];            

   var range = sheet.getRange(3,3);   // Fetch the range of cells E2:E2
   var subject = range.getValues();   // Fetch value for subject line from above range
   var EmailSubject = subject[0][0];  

   var range = sheet.getRange(5,4);   
   var message = range.getValues();     
   var messageBody = message[0][0];    


   MailApp.sendEmail({  to: emailAddress,   cc: ccEmail , subject: EmailSubject, body: messageBody, });


    }