Invoke Command Line Program from VBA Macro

I want to invoke my own program from VBA macro of LibreOffice Calc.
I tried the following
Shell (“path/a.exe”)
However, anything happened.
I tried other possible options, but results were same.
I am sure path is correct, because wrong path invoked error message.

I also noticed that
Shell (“cmd.exe”)
does not invoke command line window.

Is there any way to invoke my executable from VBA macro program?

My platform is Windows 7. I use version 4.2.2.1 of LibreOffice.
Executable was created by MinGW and it works just double-clicking the file “a.exe” from Explorer window.

Thank you.

Dear Karolus,

I really thank you for very quick response!
It worked as I desired!

I will later try Python as well.
I am not familiar with Python.

I thank you again!
Vielen Dank!

Shigeru