how to DLL to ocx

[zamaged]

i have a DLL made by C#.net 2010 and i want to use this dll in c++ to make an OCX ActiveX file in VC++ 6.0, To use it in Microsoft dynamic Nav that doesnt accept my dll file only ActiveX OCX file the Dll file is very simple that has one public function called "public string calc(string Barcode) it takes string and return string can someone tell me what should i do in c++ to use that DLL file