Requisition approval based on first line cost center

Hello All,

We came across a requirement where the requisition has multiple cost centers. However, the approval routing should happen based on the first requisition line distribution cost center.

First Requisition may have c1,c2,c3. The approval should be based on c1. The second requisition may have c3,c1,c2 and its approval should be based on c3.

How do we restrict the system to consider only one cost center for approval?

Thanks,

Vijay