multiple BW systems on SAP portal

HI,

We have real BW (NW 7.4) and embedded BW (BW activated on SAP ECC side ; NW7.4).

I found its impossible to connect more then one BW system to the portal because the alias of BW system in the URL means nothing: Does anybody know how to connect multiple BW systems on SAP portal?

We happy to pay for this consulting service.

Thanks