Yes I think that the problem was in fact that I wrote "doamin" instead of "domain", so when I used : IF ComputerInGroup("PC-CENT-SI") Kix didn't understand the domain stuff and gave me the error : Script error: invalid method/function call: missing required parameter 2! If ComputerInGroup ("PC-CENT-SI")=1 Is this possible ? And the reason why I modified the UDF is that I thought that if I only have 1 domain, the script would be faster if it doesn't have to check about the domain, don't you think ? Since I'm french (my english is not so good...) I don't really understand what you mean by recompiling the udf but I guess not, I just took the example and put away the domain stuff... Is this better answer ? But the first time I told you it doesn't work I didn't modify the UDF, I just wrote "doamin" instead of "domain"....
read above. the reason is that you removed the "optional" word from the second argument text, making it must have argument. and when you didn't pass it on your function call, it obviously errors out. so, it has nothing to do with mistyping but you clearly just removed stuff you didn't understand.
So I'm glad to see that you understand the error with my english ! By the way I still have a little problem but it's not very important since it works well anyway. The problem is that if I do : IF ComputerInGroup("ABC")=1 AddPrinterConnection... ENDIF and the computer is member of group "ABC" it works fine. But if I do : IF ComputerInGroup("DEF")=1 AddPrinterConnection... ENDIF and if the computer is member of group "ABC", and group "ABC" is member of group "DEF", it won't work... Is this normal ? It should work or am I wrong ?
well, ingroup() works recursively and it seems computerInGroup() does not. I don't really know, have never tested (just put up my AD at home) and could not care more
But the first time I told you it doesn't work I didn't modify the UDF, I just wrote "doamin" instead of "domain".... 
By the way I still have a little problem but it's not very important since it works well anyway. The problem is that if I do :
