Panels display the results of searches. To do what you want, you need to construct a search that returns the results that you want. You could have each panel based on its own base search, then you could have another search which combines the results of all the base searches to give you the result you want.
For example, you could save the search id (sid) from each base search with a token assignment in a <done> section of the search, then use loadjob multiple times (an append sections) of your combining search, to load the results of all the base searches you are interested in, and then process these to get the answer you require.
