Scott,
No, when I ground the pad while the z axis is traveling down, the motion doesn't stop (i.e., it doesn't terminate the macro).
I beginning to suspect that I don't have the correct mapping for the BOB's internal pin/terminal connection, although I've made the probe connection to match the documentation I have for Sound Logic PC-2-Route Model M2 board. Tomorrow, I'll try using a different terminal on the BOB and see what happens.
I really appreciate the responses-getting advice quickly from you guys keeps me from getting frustrated.
SF