Exporting class that has TopoDS_Solid member

Hello,
I'm working in Windows NT, and I've created a class, myClass, that contains a TopoDS_Solid datamember. If I try to export 'myClass' to another DLL, I get this warning:

warning C4251: 'm_solid' : class 'TopoDS_Solid' needs to have dll-interface to be used by clients of class 'myClass'

Sample code:
#ifdef MYDLL_EXPORTS
#define DLLIMPEXP __declspec(dllexport)
#else
#define DLLIMPEXP __declspec(dllimport)
#endif

class DLLIMPEXP myClass
{
public:
myClass();
virtual ~myClass();

private:
TopoDS_Solid m_solid;
};

How can I export this class into another DLL without receiving the warning?

Thank you,
Mike