Adam,
Try the following as your oslc.selectString parameter:
ponum,totalbasecost,status,poline{polineid,polinenum,linecost,pocost{percentage}}
You can also use the following syntax if the objects do not exist in the object structure and you just want to use standard relationships:
ponum,totalbasecost,status,rel.poline{polineid,polinenum,linecost,rel.pocost{percentage}}
Hope this helps,
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Alex Walter
A3J Group LLC
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