Hi Darren,
There are dozens of good reasons to build a mobile app, and there are also plenty of reasons to stick with a spreadsheet. What problems are you trying to solve that couldn't be addressed by putting the spreadsheet in the cloud and making it more mobile-device friendly for example? Is the app for just one person or many? For phones, tablets, or both? Does it need to be published to the Google Play Store? Does your company have existing IT platforms or services that could or must be utilised? Will there be a requirement to migrate data from the existing spreadsheet to the new app/system?
Having a quick look at your existing spreadsheet may be helpful too. If you wanted us to sign an NDA before looking at that or discussing anything in more detail that's no problem. Feel free to reach out.
Kind Regards
Jared
Free if you're comfortable with it being open sourced.