PropertyHandle :: PreviousKey - - internal feature (not documented)
Return value:  Sort key ( char * )
The sort key is passed in the internal key structure format.
Notes: 
Must be a C string
Implementation details
::Key 
PropertyHandle  :: PreviousKey ( ::Key sort_key_w=Key(), int16 kc_level=AUTO )
- sort_key_w
 - Sort key value
The key is provided in the internal key format. When necessary the key value can be converted from a string into the internal format using the StringToKey() function. Default: Key()
 
- kc_level
 - Number of fixed key component
Default: AUTO
 

