Hi,
I read your project and it is quite simple and interesting. I have built many Excel Add-In which uses their own Ribbon and Customized buttons to execute any task over the current Excel Book/SpreadSheet. In this case your project is clear and straightforward, so I think I don't have any question.
If you want I can send you some demos of an Excel Add-In with its own installer so you can have a glance on how your project will look like in the end. The Add-In is a single installer which copies the Add-In files to your PC and registers it to your Excel instance, so when you start Excel again you will see a new Ribbon appears with the Add-In features.
Regarding the payment, I will only ask you for payment release once you approve the finished project. After that I compile a final installer and send you the binaries (v1.0) and the sources of the project.
Well, I think that is all by now, if you have any question just send a message. I placed 3 days on my bid, 2 days to finish your project and one more just in case you need any modification or adjustment.
J.