I have a button in suitelet , after clicking that it should call a function and return a value . I am aware that we cannot write that function in same suitelet,so i have created a client script and wrote the function there . I am able to call that function in clientscript, but dont know how to return the value.

token_form.addButton({ id : 'custpage_refresh_token', label : 'Refresh Token', functionName : 'getAccessTokenFromRefreshToken' });

How to return the value from that function to suitelet . Can some one please provide a code snippet or sample for that ?