Hi @eniwoke 

That's a great solution thank you so much!
Our process is now as follows:
NB1 gets the tenant t-shirt size and sets the cluster_id for each size as a variable.
The notebook then loops through each tenant and using the DataBricks API updates the tasks within the job to the right cluster_id and triggers a run of the main job.

After testing (with one tenant as S and one as M), the right job was triggered twice (once for each tenat) and each of those runs ran on the right sized cluster for the tenant in question.

It's just what we were after, thank you so so much for your help!
Ally