Add cross-database dependencies?

I have approximately 50 databases, spread across 4 SQL Server instances.

I know I can find out which external objects things inside my current database rely on - but I want to do the reverse. I want to find out what all is pointing AT my current database, so that I know what will break when I try to move this database.

Is there a way to do this?

I tried adding all objects in each database, one database at a time. I eventually hung the application when I tried to get it to resolve external references, it encountered a reference to a database that doesn't exist anymore.