The problem is that there is no dictation support for the SP version of VoxCommando because the Microsoft Speech Platform does not support it. Being able to read and write files does not help you to solve this problem, unless you have some other program that converts your speech to text and put it into a text file.
VoxCommando can only understand what you say if you put all the possible options for what you say into the definition of your command. You cannot just "say anything". You can use a payloadXML to create a very large number of possible phrases but you still need to enter them all in advance.
The only way you can "say anything" is if you use a dictation payload, but you can only do this if you are using the regular version of VoxCommando (not SP) with one of the supported languages (English, French, German, Spanish, Chinese, Japanese).