Noob Question: Converting Class Levels

[Diaz Ex Machina]

In D&D3.5 there was a prestige class called Blackguard, which I'm trying to convert to Pathfinder. Aside from the myriad of problems I've already stumbled upon there's one that I really don't know how to handle.

As shown on d20srd.org under the Fallen Paladins entry, blackguards get additional class abilities based on how many levels of ex-Paladins they had before gaining a level in the prestige class. Is it possible to replicate this on Hero Lab Classic? If so, how can I do it?

Thank you in advance for your help and time.