At my new job, we sell imported stuff. In order to be able to sell said stuff, currently the following things need to happen for every incoming shipment:
I'd start by asking myself the following questions
Does the invoice have to come via email or can there be a web form where the users can enter the data? There is a easy way to put a form on google docs so you can download the response in excel format in a common format set by you. I'm sure there are better ways too.
Does the boss need to create a new spreadsheet of can you provide him with a database app where he can view your form, enter the price, check "approved" and have that fire off the process that puts it in the production db?
Can the interface to the client program be worked around? Can you have some other app call the client
Can the text to the end user be sent by you and not the client app? If so, ca you automate that part