Codepage Conversion

[<Ala...@tr...>]

Dear All
    I am using ucnv_toUChars() to convert character from different codepages
to UChars.
However, I would like to count the fail conversion times (or convert to
similar character times)
because there are no some characters in that codepage if I randomly choose
an incorrect 
codepage and call ucnv_toUChars() to convert?
    Any possible APIs or methods to achieve this goal? Thanks a lot!

Sincerely,

Alan