File association for all files on directory

Hi,

I am using PortableFileAssociator since years when I started to use PortableApps on my local machine.

I have associate the file types properly. But on Windows 7's file manager (I don't know for other versions of Windows), I have a problem. I will explain directly with an example:

I have associate the mp3 files with AIMP. When I double click on any mp3 file, it opens with AIMP. When I select multiple mp3 files, it opens with AIMP. But when I select ALL files ("CTRL+A" or selecting all files by "SHIFT+MouseClick"), it opens with "Windows Media Player". But I want to open with AIMP.

Please make something for it

Thank you!