SD- incompletion config.(plant mandatory )

Gurus,

i added plant field in incompletion at item level, when ever i try to save document it show document is incomplete with warning , but i can able to save document forcefully ,

my requirement is

i want to make plant mandatory(like sold to party in header) for item without plant document should not be save or forcefully save.

to save document u must be enter plant in item.

regards,

mahesh fulse