UD fields from Orderdtl to ShipDtl to Invcdtl

I have 4 UD fields on the orderdtl that I need to carry over to the shipdtl then eventually over to the invcdtl. The custom field map program doesn't seem to support mapping to the shipdtl or invcdtl tables. Anybody know of any other way besides a bmp? We're on 408a
Thanks