Rob Golding:
Are tags the best way to go about this?
I don't know your requirements, so can't comment.
Here's a review of MicroStation and Databases, which covers both DGN internal and external data.
Rob Golding:
i only chose Tags because i don't really know of a better solution
It's best to go for a solution that (a) you understand and (b) is exposed to VBA. Not all data models are currently possible using VBA. For example, EC Schemas (i-Models) are pretty new and a C++ API was published in autumn 2012.