Why can’t you make it global? What are you trying to do? There may be other ways to solve your problem than passing it via the function, which is, by the way, not possible.
If you can’t make it global, then other than a different solution to what you are trying to do … the answer is NO, unless …
You edit your GLUT source code and ADD an extra arg to the glutKeyBoardFunc() !!!
Or, perhaps more elegant, add a void* pointer to the end of the window structure, so you can point this to your own data structure which will be carried around on a per window basis …