Partial milestone confirmation

Hello,

I have milestone billing scenario where in partial milestone being done.

My query is when user will do partial confirmation of milestone from PS module then system should not allow user to do billing for whole amount.

Say milestone value is Rs. 10000 and confirmation has been done only 50% then user should not allow to create billing document for Rs. 10000. it should be only 50% that is Rs. 5000 in billing document.

Thanks & Regards,

Ratish