How to achieve 7z format compression?

[Gintaras]

If you can find 7z.dll documentation or header file, you can use it in QM directly without C#. But need to know how to convert C dll declarations to QM.
If you want to use SevenZipSharp.dll in QM, start from menu File / New / Templates / Scripting / C#...

I cannot help much. You can use the command line program, it is easy.