Problem passing a set like parameter in IReport

[Etantonio]

Hi,
I'm using IReport to create a doc starting from a query,
The problem is that the where in the query is something like this :

where student_name in ('carlo','ennio')

now, building the query I want to do :

where student_name in ($P{parametro_nome_studente})

but giving the value 'carlo','ennio' to parametro_nome_studente
I've an sql problem in IReport.
How I could solve the problem ??.
Thanks

Antonio