I am fairly new to okuma also, but have done similiar type things using the workshift function. you can write in VZSHZ+(or -).... whatever the difference is between the front and back. using the shift, when it hits the m02 it will automatically reset to zero at the end of the program. I think it is way harder than a fanuc but it works. if you have a book with the machine it explains a little bit. I will check more into this but this should get you started.