question from ZhanGuo mod : anyone know how to file *.bpi

http://img212.echo.cx/img212/8168/door8to.jpg

here i want to find some help with the file *.BPI
we find that this file is control the behavior of soldier attack the city ,like capture the wall , attack the door etc, but we don't know how to edit these file . could somebody tell me ? because it relate to our work of the screenshot up there . we want to let the soldier to move on the tower .and fight with the enemy .

here is our mod link , we post our works here ,
https://forums.totalwar.org/vb/showthread.php?t=48543

If you are interested in becoming part of the Zhan Guo Modding team or give us some sponsor , please contact me at the below 2 emails:
foxadams@21cn.com
waitcu@hotmail.com

The game will generate the .item and .bpi files, what steps did you do to add the building?

well , the question is not how to add the buiding , it's how to add the file *.bpi