Alllows to start a program via a registry entry, so the caller does not need to know the installation directory (and the directory doesn't need to be added to the sarch path).
Example:
dzStartViaRegistry "HKLM\Software\Scooter Software\Beyond Compare" ExePath *parameters go here*
Reads the Entry ExePath from HKLM\Software\Scooter Software\Beyond Compare and starts it. That entry (at least on my computer) points to the Beyond Compare executable regardless which version is installed.