Thanks for your query.
Well, it looks like you are using Aspose.Cells component via COM interop. Are you trying to use Aspose.Cells assembly directly via COM interop. Well, we think the better way is you should access Aspose.Cells library by wrapping it into a custom .NET component and expose this component to your environment via COM Interop. You will write a COM wrapper that references to Aspose.Cells assembly and does all the work you desire with it (e.g you may write your custom methods which use Aspose.Cells APIs accordingly), which should expose your desired methods to unmanaged code.
Since you are finding issue with registration, still not sure though, I think you may separately create a simple component/class in C# using VS.NET (without involving Aspose.Cells API), build it to generate Dll file, now try to register it using command line:
regasm.exe MyLibrary1.dll /codebase
now check if you see component in the com library list in your system or not.