It won’t be recognized as a category title that way automatically. In order to pass extra categories (i.e., more than one at a time) you’ll need to get creative. I’ve done it a few ways- prefer to use cat ids, as they’re easier to work with. But no reason you can’t work around it with cat names.
But it is custom coding- so I’m going to shift this to ‘How to’ and throw out a few ideas.
Pass the extra cat(s) as additional segments. Turn dynamic off, grab all cats, query to find their ids (main reason I prefer ids- no need for this step)- then echo those out (php parsed on input) in the category parameter of your weblog tag. Or- leave them in one seg- seperate with +, explode on the plus, do your query- echo the resulting ids.
So- no standard way to do it, but folks have worked around it in various ways.