Hi @Alias Leung
Based on my tests, Excel for Office Professional Plus 2016 does not support BIG5 function and supports ASC function for specific language, such as Chinese Simple , likes the following image.
Under the case of using Chinese Simplified, if you need to change half-width (single-byte) characters to full-width (double-byte) characters, I suggest you try WideChar function.
Here is a similar thread "Cannot find ASC / BIG5 formula in Excel 2016", you may also have a look.
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Hi @Alias Leung
Thanks for your sharing, which will help other users on Q&A forum who encounter the same issue.