[Zope] Catalog and local characters

Hello zope community Here is the problem, maybe you had it before if you're french, german, spanish.... I have a collection of objects supervised with a Catalog. Say I have an object containing the string 'ingénieur' If I search for 'ingenieur' it doesn't work.... How can I tell the Catalog to ignore the difference between 'é', 'è', 'e', 'ê' Same for 'a', 'à', 'â' .... ???? Any clue is welcome, since many of our seaches in the Catalog return nothing because of this NIL