How to setup approval hierarchy on requisition line

 I have internal requisition with tow lines both of them inventory source. I have stock controller check availability if we haven't onhand so he will change the source one line to supplier  in this case we
have one req. by 2 lines with different sources(one of them is inventory and
other by supplier sourcing).
After he approves this req. the Req. will go to the approval hierarchy Based on req. header… but we have one approval path for
each line.

thanks