How to ignore the Power Net Extraction in an LVS BOX cell

Hi ,

     I've a database with some IPs and clock tree network inside. The Power Supply for this one is distributed from TOP to each VDD/VSS Pin of std cells (used for clock tree network) and VDD/VSS Pin of IPs.

     Now, i want to extract parasitic data relating to clock tree network only (it will include : clock tree network cells + clock tree signal routing  + power distribution routing ), I've used LVS BOX to box all IPs. However, the parasitic data of Power Suppy Distribution (VDD/VSS) still contains the data of IP Power Routing.

     How can i get the parasitic data of Power Supply for Clock tree network only and ignore all the Power data belonging to IPs ?

Thanks,