Automatic sign in on a web page

There is a web page where new apartments are offered to the one who signs in and accepts the apartment. I want a software to be developed that should sign in to the web site (I will give the username and password), it should check at least once every second (or even better, ten times per second) if there is a new apartment offered, if so, then it should take the apartment. This is today a manual process: if not logged in: 1. I come to the site [login to view URL] and log in ("Logga in"-button), 2. I write username and password when logged in: 3. check if any new apartments are in, click "Lägenheter" 4. On the list, if any new apartment is in, then click on it, 5. Click "Anmäl intresse"-button. And this is the last step. Repeat the above every second, or more often. This software could be installed on your computer, or as a software on my computer (Mac), so I can run it. You can give me suggestions here. The only thing I want to manage is the username/password input.