Add new key in transformation

Hello BWers !

I'm using a transformation between DataSource 0CRM_POSITION_ATTR and ATTRIBUTES of 0HRPOSITION :

(RSDS 0CRM_POSITION_ATTR D1CCLNT200 -> IOBJ 0HRPOSITION)

I would have 0DATEFROM Field from 0HRPOSITION as a key into the transformation.

Can I do that, and how ?

Thanks for help.

Vince.