Header conditions should be editable

Hi Gurus,

Need your help in handling the below requirement.

client requirement: One header condition should be there for manual fixed amount discount and the system should allow it only in Invoice...

For this I created a new header condition type with condition category L and manual entry has priority "C"... maintained requirement "24" to get it triggered automatically in invoice only...

This condition is getting triggered into invoice automatically but it is in grey mode..

here the user want to give value manually every time...so it should be in editable mode..

Your valuable suggestions are highly appreciated..

regards,

Siva.