Hi Krishna,
well, that solution woudl require exact definition of when this message should come up and then straight rule config, which anybody with basic rule config knowledge will be able to do for you. So, just ask ypour time management consultant.
However, I would encourage you to explore a cleaner solution:
why don't you use Core Working Time in your daily work schedules. if you set that up to cover, say, 6 or 7 of teh 8 hours day, then you'd get a message from SAP standard, if the employee is away furing some of teh core time.
kind regards
Sven