Setting up extension field on New: Base Price List screen

Hi,

I want to set up an extension field on New: Base Price List Screen (WC: Product and Service Portfolio ->Pricing -> Price List -> Base Price List -> New -> Item Level) but I am not sure where/what business object should I extend to set it up on screen. Any suggestions on how can I extend this thru SDK? I mean what extended business object should I use? I will be putting up a computation so I need to set it up thru SDK. Any help would be greatly appreciated.

Thanks and Regards,

JM