I'm not sure you can do what you seem to be wanting to do. You see http connections (and indeed most network based connections) are streaming connections. That is there is no way to seek, or request a particular part of the file. You simply have to read it from start to finish.
If you're trying to do what I think you're trying to do, I would suggest you load it into a bank first.
If you're trying to do what I think you're trying to do, I would suggest you load it into a bank first.