Unicode edit masks can be used similar to code page edit masks. The difference is that the edit mask is always stored in Unicode format.
This allows you to specify edit masks with mixed characters from different code pages and assures that always the correct character is displayed, independent of the installed system code page.
For the general usage of edit masks, see Edit Masks - EM Parameter.
For information on the session parameter
EMU - Unicode Edit
Mask (in the Parameter Reference).