Dont sweat it too much.
The script in code box below works pretty well (based off Corno_1's, just needed a way to stop player moving), dont think you can disable the w.a.s.d and arrow keys (doesn't for me anyhow), so dropped those out. Not sure its your intention to disable any keys since you may find you want to crouch, whatever, you can always remove these from the script.
Normally right mouse button is reserved for zoom/ironsights with weapons so no idea if going to conflict with things when you equip one, test it out and see how it goes
Put the script into AI Main of a trigger zone, place the zone anywhere in your level.
;Artificial Intelligence Script
desc = Move player RMB
;Triggers
:state=0,always:jumpkey=0,crouchkey=0,state=1
:state=1,mouseclick=0:plrforcemove=0
:state=1,mouseclick=2:plrforcemove=100,state=2
:state=2,mouseclick=0:state=1
;End of Script
I also tried the middle mouse and as said it doesn't function, sure I read it was in one of the updates, my bad.
I'll be honest with you, its pretty cool idea, though it might be specifically suited to certain types of game
Might even use this myself.
Awesome! Its one of those threads.