Modifying line item price in Purchase Order

Question

Hi guys,
Need your help regarding pricing modification in purchase order.  I know the below explanation is quite long enough, but still if you can look into it and put some thoughts:
The price picked for a line item from PIR, needs to be modified depending on total price.
Say for example, in a PO there are two line items
Mat1     10PC 10 usd/1pc
Mat2     10PC 20 usd/1pc
so total price for PO goes as 300 usd.
Now, if PO price exceeds 250 usd a different price needs to be picked from a custom table for line items. Say it should now become 8 usd/1PC and 18 usd/1PC for Mat1 and Mat2 respectively.
So, after entering PO items if the user presses the 'check' button, new price should be picked, as per the above example the new lines should be shown as
Mat1     10PC 8 USD/1PC
Mat2     10PC 18 USD/1PC
so total price for PO goes as 260 USD.
Hope I've made you clear about the requirement.
Now, what we are able to do so far is:
We have used the 'check' method BADI 'me_process_po_cust'. And we are calculating the total price and changing the item conditions.
But it's not reflecting on the me21n screen even after execution of the 'check' method successfully.
It still shows the line items as
Mat1     10PC 10 USD/1PC
Mat2     10PC 20 USD/1PC
But, now if we make any changes in the line items (say we add the requisitioner name) and hit ENTER the changed prices are reflected. And the items become
Mat1     10PC 8 USD/1PC
Mat2     10PC 18U SD/1PC
This is a thing we are stuck into.
Please express if you have any idea how to come out of this issue.
Thanks in advance.
Anupam

Answer 1

Hi Anupam,
Flow Logic of the screen.
PROCESS BEFORE OUTPUT.
  MODULE STATUS_0100.
  LOOP AT ITAB WITH CONTROL TABC.
  ENDLOOP.
PROCESS AFTER INPUT.
  LOOP AT ITAB.
    MODULE READ_TABLE_CONTROL.
  ENDLOOP.
Write the read_table_control module like below
MODULE read_table_control INPUT.
   MODIFY itab INDEX tabc-current_line.
   "The above will update the entered data on table control
ENDMODULE.
Kindly check if this table control gets updated in PAI or not.... if not... try to find an exit where  this can be done on PAI.....
Regards,
Deeba