Excel Spreadsheet to be re-designed, and add new features

As a seller of personalised items online, I have designed a simple spreadsheet so that I know how much profit each item makes. I sell on 3 sites, and the profit is different on each site.

I'm now looking to employ someone, and need this spreadsheet modified so that they can enter the items they have personalised each day. From this, I can see how much profit each order they have completed has made, and how much profit they are making.

They employee will not see the profit of each order. They will merely enter items they've personalised from a drop down list, along with information such as the postage costs. The profit data needs to be stored on a hidden worksheet that they cannot access.

I have attached a sample spreadsheet to give an idea of what is required. I'm happy to have a conversation if you're interested so I can take you through exactly what I'm looking for.