Type comType = Type.GetTypeFromProgID(ProgID, false);
object comObj = Activator.CreateInstance(comType);
// и далее вызываем методы
comType.InvokeMember("DoLongWork", BindingFlags.InvokeMethod, null, comObj, null);

  IHookCallback = interface(IDispatch)
    procedure ServerHook(DoStuff: integer); safecall;
  end;

procedure SetupHook(const Callback: IHookCallback); safecall;

// COM мы уже создали раньше
comType.InvokeMember("SetupHook", BindingFlags.InvokeMethod, null, srvObj, new object[] {SomeClass as IHookCallback});

Exception has been thrown by the target of an invocation.

Specified cast is not valid.

// Interface: IHookCallback
// Flags:     (4416) Dual OleAutomation Dispatchable
// GUID:      {3586BB08-CEDD-466C-85E6-5CEAE4DFB15F}
// *********************************************************************//
  IHookCallback = interface(IDispatch)
    ['{3586BB08-CEDD-466C-85E6-5CEAE4DFB15F}']
    procedure ServerHook(DoStuff: SYSINT); safecall;
  end;

    [TypeLibType(4160)]
    [Guid("3586BB08-CEDD-466C-85E6-5CEAE4DFB15F")]
    public interface IHookCallback
    {
        [DispId(201)]
        void ServerHook(DoStuff: integer);
    }