Return the character used for columns in R1C1 format
TCHAR GetColumnPrefix( ) const;
Returns the character used to prefix column values in R1C1 format, in the language that was set when Excel was started.
In English, the function returns upper-case 'C'.
If the user language is changed while Excel is running, the character returned by this call may no longer be valid. The character is set during the XllOpen event, and is cached in the CXllApp object for its lifetime.
Note that this function can be used during worksheet functions, but CXllApp::GetInternational, which returns an up-to-date value, cannot be called during worksheet functions.