Create a dynamic data expression and select the list of things you want to work with.
Then use the :format as text operator.
It will look something like: do a search for Users: format as text with the details within it.
This will let you create a dynamic expression per item in the list selected and also define a delimiter (a character or string that separates each of these items). Putting a comma here would separate your dynamic expression per item by a comma for example.