Dear Deepak,
The behaviour is standard after you manual change the gross price,the GR date will change to manual.
In standard, the supplementary conditions are linked to your gross price PB00 and it need to
determine accordingly as defined in pricing procedure. Once you change the gross, the linkage between them will be not relevant anynmore and thus price date as GR date will be not relevant as well.
Therefore, you get it change to manual automically.
Regards,
ian Wong Loke Foong