Way overdue for this, but ... create a DBSchema file for your "TransactionHistory" database project. Put it in some shared location in a level above the database projects. You can usually get this if you can successfully build the project

C:\DatabasesC:\Databases\Schemas <-- This folder for your shared schema files

C:\Databases\TransactionHistory

C:\Databases\MyProject1

C:\Databases\MyProject2

...

In your project, right-click the "References" folder and choose to add a Database Reference. Point that file to the DBSchema file in your Schemas folder. Having this as a reference will eliminate most of the reference issues. I found that I needed to also add the schema to the table names referenced to get them to work, but it will allow 3-part naming conventions for referenced databases.

This works for VS 2008 and VS 2010. However, if you have the freedom to upgrade to SSDT SQL Projects, I'd say it's worth it. You'll need to switch out your DBSchema files for DACPAC files, but there are a lot of small changes that make them much nicer to use over the older VS2008/2010 projects. Referenced projects would work in a similar manner.