I just tried it out now and actually it was pretty confusing. Maybe the interface is broken on my version of Steam but if you click the mouse on the box to change the type of updating, you can't scrow down and nor does a drop down box appear. You have to click it then press the down arrow on the keyboard. That is quite confusing and my first thought when the mouse didn't work was that the update mode was locked as automatic and couldn't be changed. It also seems that when the update mode can be changed, it can take up to 10 seconds or so to change. i.e. lag. Then I tried restarting Steam and put it in online mode and it seemed to work much better. This time the drop down boxes appeared and there was no lag. So, you can only change the auto updating in online mode? I tried to reproduce what I saw earlier in offline mode where I was able to change the setting but I can't now. It's not rocket science I guess, but it was a hassle because I hadn't done it before.