Hi Yusuff,
In schema TM04, the standard sub schema TW15 can do this for you.
I wouldn't recommend you to go for approval of overtime hours after they have been calculated. Standard SAP provides seamless integration of time with payroll.
Time types and overtime wage types get refreshed with each time evaluation run. It isn't like payroll where you have the concept of retro payroll.
Hence, if you have retro time evaluation run, you won't be able to know from Table ZL or Table ZES if the overtime hours have changed or not in retro run. So, this will require some custom development.
I hope this information is helpful for you.
Thanks and regards,
Vivek Barnwal