hy, pls check attached osp300pdf's, about using "osp io monitor.exe" ( located on right toolbar ) :
... VIRD[1210]=1 means door is close
... VORD[16]=1 means that machine is in lock mode
* examples are for lathes, but mills share same osp, so there are similarities
different machines have different signal maps
you can check status for single block, block skip, override value ( for example you can check if override is between 80 and 120% ), monitoring, coolant, etc / kindly
ps : if you wish to see what others have done, then search for vird & vord on the forum; i believe that maybe also vdin & vdout can be used, but i don't have experience with those