Saving sub assembly within main assembly as one stl file.

Hi,

I am trying to save out stl files to be imported into an animation program "Unity".

When I save the main assembly as an stl it creates a large amount of files as it saves all the parts in the sub assemblies as separate files. The sub assemblies that do not move can be saved as one stl file to reduce complexity at the other end.

Is there a way to specify for a sub assembly to be saved as one stl file when saving the main assembly as an STL?

thanks in advance

SolidworksAssemblies