We hope that Michael has applied TimeOff through my time off screen. So if that the case you just have to disable them
Lock Submitted Records In TimeOff. You can do that by following below steps
1) Open Master Data–> Advanced Settings–> Preferences
2)Go to TimeOff SetUp Tab Uncheck the Lock Submitted Records In TimeOff option which will allow the employee to Edit the TimeOff which is submitted and Not Approved so that Employee can Edit that particular TimeOff project.