CJ20n - User Exit to pass partner details

Hello,

I am working on screen exit in transaction CJ20n. My requirement is to add partner details(SP, SH, BP,PY) fields to the new screen at the wbs element level. Values for these partners needs to be fetched from partner tab which user will maintain at the project definition level.

I am searching for an exit which will help me to fill the partner details.

Please do help me out in this regard.

Thanks,