~ - replace tilde(~) with other symbol if your string contains it.
=IF(ISERROR(FIND("\",B1)),B1,RIGHT(B1,LEN(B1)-FIND("~",SUBSTITUTE(B1,"\","~",LEN(B1)-LEN(SUBSTITUTE(B1,"\",""))))))
=IF(ISERROR(FIND("\",B1)),B1,RIGHT(B1,LEN(B1)-FIND("~",SUBSTITUTE(B1,"\","~",LEN(B1)-LEN(SUBSTITUTE(B1,"\",""))))))