A couple of options.
1. Why not just let it open a new instance, then just close it at the end of the JMP Script?
2. put `//!` at the beginning of the script and just open it. It should open in your currently registered version of jmp and auto run.
3. save the .jsl as a .jrp and it should do the same thing as 2.
I personally prefer non-interactive things like this to do 1 because then I can confirm that JMP closed appropriately in powershell so that I can give better console error messages.