BIML - How do I create table metadata from two databases?

I have been using the Automated Staging video as a tutorial and seeing if I can make it work for me.

In the example it uses a single DB as source for the tables.

I want to extend this to 2 DBs.

So I figured I need to be able to loop something with sourcename and tablestobeincluded. Can I define a custom class ? I can't get it to work, nor can I find any info if its even possible.

Then I came across CallBIMLScript, which sounded like what I needed, but it appears it can only work within <Package
> tags, and I am doing it for <Tables>

What is the best way to do what I need?

Thanks

Jon