Yes it's possible, but I'd recommend using Selenium WebDriver as it's the current version. Selenium RC is very old.
Using Selenium WebDriver:
driver.navigate().to("http://aut/login");
driver.... // login logic like setting the user/pass clicking login.
...
driver.navigate().to("http://somenewurl.com");
// continue testing here...
If you are adamant on remaining with Selenium 1 (which i could understand if you already have a big suite in it..):
selenium.open("http://aut/login");
selenium... // login logic here
...
selenium.open("http://somenewurl.com");
// continue testing here.