Change Voiceover language for a custom NSView for an OS X app

I have a custom class that derives from an NSStackview that contains 2 buttons. The 2 buttons are inaccessibile through VoiceOver and the stackview itself handles the button actions. (Clicking the main button and opening more options on the 2nd one). This is through NSAccessibilityMenuButtonRole.

I have overriden - (NSString *) accessibilityValue of the custom class to get voiceover to read the description I need. However I'm trying to support mixed languages too.

Is there a way I can get an attributed string to be returned instead of a plain NSString for the voiceover client. This way I can use NSAccessibilityLanguageTextAttribute.

MacOS doesn't support accessibilityLanguage attribute like iOS!