Custom fields in porftolio analyzer view

[Haris]

Hi,
I'm trying to add a couple of custom fields to portfolio analyzer view
following the OLAP Extensions guidelines I've downloaded from microsoft.
The aim is to add the task based 'Work Variance' field and a custom defined
'Threshold' field, defined for specyfication of a threshold level, and create
a custom view in portfolio analyzer. Since these fields are not available in
the fields table, I believe I'll have to get them included by extending the
cube.
Any guidelines regarding this would be greatly appreciated.
Looking forward,

Regards,
Haris