Approval process on total requisition amount on PeopleSoft

Can any one help to find out how the requisition approval can be routed through  based on total requisition amount.  I could do the set up only line level amount.  Our scenario :  A requisition has 10 lines and each line has $5000.  The total requisition amount is 50000.00.  The requisition does not route to next approval level as each line is within in the range of first level approver amount. Is there any way to do the set up  to calculate total requisition line amount and process  approval workflow  based on that amount?