Gianluca,
I think I've run across the same limitation, and I've been revamping this script from being process-based to being lock-based. I wanted to add the intra-query parallel processing items, and was having trouble.
I posted a newer script over the weekend, and thanks to Mark's code below, it looks like I'll be having a newer version yet soon.
Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes