Progress Bar linked to External App

Problem,

I am trying to write an application with a progress bar that will follow the progress of an external command-line application. I'd like the program to accept the 'percentage complete' value reported by the application and scroll it the progress bar. The external program is imgdeploy.exe, which is Microsoft's command-line imager from ADS 1.x. I also have to write this in VB6 so it can work in a PE environment. Ideas?