Need math channel function for: time elapsed since start of "TRIGGER"

I have a digital meter with Value Type: Elapsed Time

But this is the start of the Armed condition not the trigger. So in my case when analyzing the data file, the start of the file at 0:00.0 shows an elapsed time of 188.25 (seconds from armed)

I need this to be ZERO or start of trigger.

In the math channel formula there's a function for TIME; So I created a math channel with the formula: "time-188.25"

This provided a workaround but I have to create a math channel for each data file since the elapsed time between Armed and Triggered conditions are different.

Is there not a simple function for start of Triggered, or Storing?

The ACQTIME and TIME function description implies different behaviors (/storing) but they both have the output