We use a stand alone post processor, we create the toolpath in pro then save the cl data as a .ncl file, the processor then converts this file to the machine readable file. Another option is to use another software all together to creat your tool paths ie, icam which will post the files for you. It all depends on how much you are willing to invest.
I worked with ICAM and Gpost for almost five years and never got a 100% non-editable posting. I went with a third party company a little over a year ago thru one of var's and I now have a post that requires no editing after posting but also does a lot of my work for melike subroutining, and what we call sorting. I could not be happier.
Almost sounds like you are comming over from Surfcam. That is only because that is the only other Software I know that uses the term Mpost. If you want to use Mpost you could use the utility apttoinc and post it thru mpost (if that is what you are using). You could create a mapkey for that
Asfar as posting is concerned I have used G-post and Campost (Icam). I have developed all my own post (G-post as well as Campost).
I am very happy with Campost (have been using it for years when they werewith PTC). Does everything for me even subroutines. Of course you would need to configure the post yourself even with G-post. There are some sample post up on PTC-site. However you would need to tweak them to your liking.
I do use Campost as a standalone post, since I use it with ohter Cam packages as well and I do not have to have Pro-E running to post and I am very happy with it.