Hi Zahid,
I meant, from HANA db of BW, create an SDA connection to HANA of ERP. Then create a virtual table(for the tables in ERP on HANA) in the HANA of BW and create your calc. views. In the modeling tools, just attach the underlying HANA db of BW. Then create a composite provider and add the calc view built on the virtual table along with your BW providers. Of course you cant add the ERP HANA db into the BW project and thats not the intention.
Best regards,
Edwin