Could not install header

Respected Proxmox Staff and Users,

I'm in the middle of installing VirtualBox on my Ubuntu SS 13.10 (run at OVZ) and i got stuck cause it keeps asking for installing pve header :

trying to install but not found the package

root@SvrVMBackup:~# apt-get install pve-headers-2.6.32-27-pve
Reading package lists... Done
Building dependency tree
Reading state information... Done
E: Unable to locate package pve-headers-2.6.32-27-pve
E: Couldn't find any package by regex 'pve-headers-2.6.32-27-pve'

Any one knows how to install and get the file?

Thanks alot in advance

Kind regards

Xen