I'm wanting to develop an app for one of my jobs (7Up stocker), I just don't know how to do it. This is what I need the app to do:

After I scan the item, I need it to let to list the product (ex. 7Up 2 Liter), allow me enter a quantity, and list it all to send in an email for the orders I make, much like a hand scanner they use at Walmart or something.

How might I go about making a such app or is there one out already that I can do this with?