Selenium using Python: enter/provide http proxy password for firefox

I want to use selenium with a proxy which is password protected. The proxy is not fixed, but a variable. So this has to be done in the code (just setting up firefox on this particular machine to work with the proxy is less-than-ideal). So far I have the following code:

fp = webdriver.FirefoxProfile()
# Direct = 0, Manual = 1, PAC = 2, AUTODETECT = 4, SYSTEM = 5
fp.set_preference("network.proxy.type", 1)

fp.set_preference("network.proxy.http", PROXY_HOST)
fp.set_preference("network.proxy.http_port", PROXY_PORT)

driver = webdriver.Firefox(firefox_profile=fp)
driver.get("http://whatismyip.com")

At this point, the dialog pops up requesting the proxy user/pass.

Is there an easy way to either:

1. Type in the user/pass in the dialog box.
2. Provide the user/pass at an earlier stage.