Hi, Sanchi Sharma!
First of all welcome to Chandoo's website Excel forums. Thank you for your joining us and glad to have you here.
As a starting point I'd recommend you to read the three first green sticky topics at this forums main page. There you'll find general guidelines about how this site and community operates (introducing yourself, posting files, netiquette rules, and so on).
Among them you're prompted to perform searches within this site before posting, because maybe your question had been answered yet.
Feel free to play with different keywords so as to be led thru a wide variety of articles and posts, and if you don't find anything that solves your problem or guides you towards a solution, you'll always be welcome back here. Tell us what you've done, consider uploading a sample file as recommended, and somebody surely will read your post and help you.
And about your question...
It sounds as it'd be more natural to implement such control within your system (if you're talking about an application or program), or from a timesheet software, or into and as a screen saver/lock feature, rather than doing it in Excel... unless Excel was always running and a certain workbook always opened. Am I wrong?
Regards!
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