thanks Erel,
I read Android USB is slave device, my untested idea is to make it pretend master and act as such, please tell me to stop if this is a pie in the sky.
the main idea is to fool the usb by initiating the connection from the phone rather than from the device, then in the same connection string I embed the command I want to send to the external device, which I beleive will be sent by the usb as an answer to a command apearing to be coming from that external device!!