DBMS_SCHEDULER 11g chain affinity

Oracle 11g 1.0.7.0 RAC on 2 Windows boxes.  

I have managed thru the use of PSexec to be able to call external procedures using dbms_scheduler. I have set up a chain with a list of programs but the ones executed on instance 1 fail while the ones executed on instance 2 succeed. I have looked at the documentation and not found a way to restrict the actual programs to a particular node, only job that calls the chain has an affinity attribute. Can anyone suggest a method to accomplish this while I determine why instance 1 hates me?  

Thanks,

Chris  

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