SetLanguageDowngrade(TInt aIndex, TLanguage aLanguage);

What exactly this function does?
What is the use of TInt aIndex parameter?
How can I use this function to switch the help file used in the application without changing device's language?

FYI:
    -the application is developed under 3rd edition S60
    -the application implements multiple language UI with the possibility to change them while running
    -the help files to use are all placed in \resource\help and named MyApp.h01, .h02 etc...
   
    -on 2nd edition I placed only one Myapp.hlp file in \resource\help and I was programatically replacing it with the corresponding help file when switching UI language in my application, but now on 3rd edition I need TCB capability to alter \resource\ folder content, capability I don't have and cannot obtain easily.