editing of zcustom fields in ME23N on change

i have developed zcustom fields in header lavel in ME23N thru userexit MM06E005.but when i click on change, all fields comes in change mode except those zfields.

how can i sink my zfileds with those standard fields on change?

or how can i put those zfields in change mode on click of change from me23n.

same think haapens on ME22N , after save, all fields turns grey(disable) mode except my zfields.

how can i sink my zfields with standard fileds?