Hi Neha,
Please have a look at SAP Note 912473 - Brain 039 in customer exit variables for hierarchy nodes. I think that the following part is relevant in your case:
Foreign characteristic nodes:
You must enter the technical name of the InfoObjekt of the required node.
Furthermore, you can also have a look at how data is stored in the Hierarchy table /BI0/H... It can give you a hint which Characteristic to use.
Best regards,
Sander