Blending is the correct machinery for looking up facts on a separate datasource. If the size of the relationship(s) is too large, consider a bit of ETL to flatten the data with all the facts possible.
thanks for your quick reply. Sorry I'm a bit of a novice, whats ETL? Do I need some special software to do that or is it doable within just tableau and excel?
In computing, Extract, Transform and Load (ETL) refers to a process in database usage and especially in data warehousing that: Extracts data from homogeneous or heterogeneous data sources. Transforms the data for storing it in proper format or structure for querying and analysis purpose. People mostly use Datastage ,informatica for performing the process.