Download Report seperated by User Id (no replies)

Hi

I want to seperate my download statistics in Piwik by an user id. To reach the goal I added in my tracking code a custom variable named user id. It works fine as far as I can see it in the report part concerning the custom variable. But how to seperate the download statistic by my added custom variable? I tried to use the segmentation method but it failed. Does anybody know how to realize it?

Example:

Client ID | Document | Downloads
----------------------------------------------------
100000 | AGB.pdf | 1
----------------------------------------------------
100001 | Vertrag.pdf | 1

Cheers

moe