Exit for VA01 Milestone Addition in Billing plan

Hi Experts,

I have one requirement for Tcode VA01..While addition of milestone in Billing Plan :

Problem : When we create the header billing plan in a ZPFM (custom sales order type) the “Fixed Date” is set to a default value of “0” (Fixed date not copied from milestone). This makes sense when the plan is manually entered. However when the billing plan is actually copied from the milestones, the “Fixed Date” flag stays “0” and each line of the plan needs to be manually changed to value “1” (Planne/Actual Date from milestone).

Need exit for this to automatically update the value.

I don't know the exit name,

plz suggest the exit name , its very urgent.

Thanks & Regards,

Deepak