Set variable with Apostrophe

Hi all,
I have a problem with my Project. In my language there is a lot of letter with accents.
For other reasons I can’t use these letters directly (eg ù) and I have to sobstitute them with the apostrophe (u’).
So when I have to set a new variable (eg Gesù christe becomes gesu’ christe) the system doesn’t set the variable. How I can solve this problem?

Sorry for bad english.
Best regards,
Eros.