How to control footer in the report ?

My report is having body PurchTable  having two section groups One Purch Line and another for VendPackingSlipJour

So for each PO am printing all lines and all packing slips.And i have taken footer section under PurchLine

so that after all lines finished  total should be displayed.

For e.g PO :1000001

item1 10

item2 20

total 30

packslip1

pakingslip2

Now the problem is if PO has  packing slip then footer is displaying after  packslips section and if it has no packingslip then footer is displaying after itemline section correctly.

I want footer to be displayed after itemline section,no matter if it has packing slip or not.