Hi,
If you have to post data from one Model to another Model, using a BADI then you can write your code in the custom enhancement - UJ_CUSTOM_LOGIC.
But if its is simply data copy from a model to another then you follow -Arnold Warhonowicz
using script logic. Follow this post - http://scn.sap.com/thread/3381858
Regards,
Bishwajit