Trigger Timer (and GPIO) from SAADC

I've been struggling with this for some time now and no matter how I approach it I can't quite get it to work.  I'm essentially looking for something like the "maximum performance" example, except at the end of each sample I need to assert a GPIO and then clear it a few microseconds later.

I have tried tying the NRF_SAADC_EVENT_RESULTDONE to a timer start task, but this doesn't seem to work for some reason.  Can someone suggest a better approach or show an example of starting a timer in this fashion?

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