revise PGI for order type

Hi all,

i have issue when revise PGI for order type

I want system refuse do this before cancel billing request .

process

1- I create service order IW31

2- Add component to order

3- PGI from MIGO

4- Create Billing Request from DP90

5- Revise PGI from MIGO without cancel billing request

I want system refuse revise PGI if i create billing request .