VA02 ,propose the value for VBAP-bedae and save

Hi experts,

I have a situation, when i goto va02 transaction the field vbap-bedae should show a value based on the requirement, if the user saves the document then it should save the proposed value if user does not save the value revert to the precious value.

I can propose the required value by making the changes in userexit_MOVE_TO_VBAK and modify xvbap[] but if the user doesnt save proposed then it should restore to its old value.

Please let me know how to accomplish this requirement.