Setting email notifications

I'm sure this is very simple, but it will be the first attempt at scripting and I'd appreciate someone pointing me in the right direction. Our application is a product inventory. Each product has a Category, Group and Item Name. There is a Reorder Status field with a dropdown selection of either OK or REORDER. When the user selects REORDER, I want to app to send a reorder email specifying when the record was changed and the item Category, Group and Item Name. Any assistance is appreciated.

Thank you.