Hey, sorry for the vagueness!
PostHaste is designed to be called
from BTV. Basically, instead of putting your programs in the CustomPostProcessing.xml file, you put them in PostHaste. Then, you put PostHaste.exe in the CustomPostProcessing.xml file.
BTV will pass the filename of whatever video is to be processed to PostHaste, which will then run each of the programs you configured in PostHaste, passing the filename to each in turn.
The point of this is that PostHaste allows you to hide the UI of the post processing programs (like comskip for example) which might otherwise steal focus or cover up the BTV application. Instead of having BTV run the applications, PostHaste does it for you.
Let me know if you need any more help.
Sorry it took so long to post this.