Hi Nikhilesh,
According to the available documentation you can do this derivation only if the storage type of your main entity has storage 1 and the other entity storage type 4. In your instance both are of type 4 and thus will not work.
The only solution is to do Cross entity derivation rule.
The documentation should hopefully provide some assistance.
http://scn.sap.com/docs/DOC-15077
Regards
Riaan