Answer
You cannot make this in one sweep, but you have to split this up into two sweeps
and the trigger offset. Then you can measure the falling edge.
Please keep in mind that you also must measure the rising edge, as the
trigger event and the sweep have an offset.
First, you have to measure the offset at the rising edge.
Start a video trigger and watch the rising edge of your pulse signal.
Now select a level for the video trigger point (for example 50 % level of rising edge).
This will be your new trigger point.
Then select an offset delay of 595 ms.
Your display starts 595 ms after the video trigger and you should select 0.5 ms per division.
Now you should see a falling edge at the end of the display screen (screen starts at 595 ms and ends at 600 ms).
If you do not see the falling edge and the level is high, you can use a 598 ms offset. If the level is low, then you should use 592 ms, and so on.
The accuracy will be approximately 100 times better than with the entire 600 ms pulse displayed on the screen.