Long story short, you can't get there from here.
With an analog scope, you can only see things that are repetitive in nature on the screen for long periods of time. Repetitive signals continually "redraw" themselves, so they look like they are standing still on the display. To stop time on an o-scope, you need one with digital storage. These scopes sample the data, save it in a memory buffer, and then write that data to the screen. When you tell it to stop time, it simply writes out the data in the buffer to the screen, until you tell it to do otherwise.