How to create surfaces of strucuture in a DPD simulation box?

Hi everyone 
I use mesocite module and run DPD simulation. And I want to create surfaces of the system , and get snapshot just like this:User-added image
I know that, in a molecular structure, we can use "atom volume & surfaces" tool to get the surfaces. But when the DPD.xsd file is active ,the "create" button in "atom volume & surfaces" dialog is grey and unavailable. 
So how can I create the surfaces of a DPD simulation structure like the image above?
Thanks for answering

Fang