Xgen-lists

I am working at Xgen program and I am using lists with a 'multiple'
listtype. The problem that I have is that when I select more than one
elements from the list, only the first one is returned as a value of the list
and the rest are ignored. The listseparator is either a " " or a ",". It
doesn't seem to be 'valuestring's ' fault. Can anybody help?

Thank you.