CMP does not allow you to change the version number if you are doing it in Open for Edit.
To do what you want, open the file for for edit in Explorer, create a new folder on your desktop and copy paste all the details from the editing folder into it. Change the version number then drag and drop the folder into the main CMP window, then Commit.
This works with CM3.3 but I don't know whether CMP will allow a version higher than itself if that is what you are trying to do.
Peter