How do I limit the diskspace and data transfer for each site based on WHMCS packages?

We have the WPMU main site on a VPS (OpenVZ Container). We also have WHMCS with the WHMCS Multisite Provisioning addon installed.

Is there any other plugin/addon/module that can monitor the usage (data transfer, diskspace) per enduser site? Also be able to limit the disk and data transfer usage per site via WHMCS?

Thanks