I don't know much about vjoy, and less about coding.
Hopefully someone who knows more than me can address this. I dod know there are multiple people here who use vjoy.
One other thing you probably already tried - is is possible to set vjoy as your preferred controller?
Here is how i did that with a controller in Windows 7:
Start > Devices and Printers
Right click on vjoy and select Game Controller Settings (not sure if this is even possible)
Select Advanced
Choose it as the Preferred Device in the drop-down and click OK
For Windows 10 I opened settings and searched for controller settings to find the same tool.