JFYI, what I often do for those functions I am not already familiar with both in Italian and English (it doesn't work for really all functions) is to use the English original I find in (the English version of) Spread32 (an extremely small Excel compatible program):

http://www.byedesign.co.uk/

then save the worksheet and re-open it with the Italian Excel, since the functions are actually saved internally as an "ordinal" (or whatever) and interpreted by Excel in its "local" language.