Thanks Jared, Chris,
I was thinking about enhancing my code with this multhreading option, but as I'm not a VB expert, I tried to use shortcuts 
so I will update my code
for this other point, it still brings me some questions... ok, when I unpark or park my mount, I can also select an option in SGP which will also open/close the roof BUT what happen :
- if my mount is unpark and I click on "close shutter" in SGP ? apparently I still can move my mount which is not good for me ...
- if the shutter is in error state, what happen if I try to nudge the mount (I can not test it in simulator mount, and do not really want to try it in my remote observatory ...)
for me an option like checkboxes where I can choose what to do in the different state of the shutter like :
do not allow to move the mount as long as the shutter is not in "open" status (or maybe even more granular)