I remember making something similar before I started with Cognos. I'd get dozens of emails a day and wrote scripts to dump everything into an Access database, scripts to construct reports, and scripts to email stuff. I felt so incredibly proud of myself for doing it, and at the time it was an impressive piece of programming. 11 years later, knowing what I know now, I'd like nothing more to reach back in time and smack myself in the head. The error rate was down significantly from when things were done manually, but errors still snuck in. The solution required my computer to be on and available 24/7.
The first thing to consider is the source of information. From what you've written it looks like you have two:
1. Vendor (received as an email)
2. Internal (processed in Cognos)
Ideally the vendor should be able to directly or indirectly load their data into the same database (not necessarily the same table) that your Cognos is pulling from. Directly would be granting them write access to some tables. Indirectly might be allowing them to save files onto an FTP site and having an ETL run to load those files into your database.
The keyword here is ETL. Having a well governed system in place to retrieve, validate, load, and integrate vendor data into your own system is key to ensuring consistently valid results.
That being said, I am very well aware that setting up a decent ETL may be difficult or impossible, so let's look at other possibilities.
1. Connect Cognos to your Access database. As long as the database is stored on a network drive, this should work. Set up an event to check for new data and run the report as necessary.
2. Use local data in report studio. Upload data and run the report manually.