I don't have NON-ENGLISH version for EXCEL.. so fully untested and blind shot.. requesting to confirm if below UDF works for you..
paste the below code in Excel > VBA (Alt + F11) > NewModule
[pre]
Code:
Function TestMonth(mnt As Range)
TestMonth = Application.GetCustomListContents(4)(Month(mnt))
End Function[/pre]
if In A1 = 17/5/2013
then in B1 write formula as =TESTMONTH(A1)
Thanks you all, My stupid solution was to use choose and manualy enter the month name but the [$-409]mmm is exctly what I want; now the month name is always in english.