DrLevine,
Your question is a little vague, so i'll try to answer with a general discussion.
First, try to sketch the process.
Second, write down what you are doing.
Third, add the I/o to your descriptions.
So my question is, what are the magnetic sensors for and where are they used?
What are the 4 stops that you are referring to and what are they used for?
regards,
james