GRBL and UGS custom path and dwell code

Hello all, still working on my first build.

I have done some searching on google and through the forum, and I can't seem to find any info on this so thought I would ask it in a thread of my own, please direct me elsewhere if this is something commonly known

I am using GRBL and universal G-code sender to create a 2 axis CNC bed with an Arduino UNO, in order to hold a sensor suite and traverse it across a plate. I want to move across the plate in a snake pattern, stopping intermittently to take a reading with the sensor. I am not sure of the commands or how to make a custom pathing like this, so far I have just used simple commands to send the X and Y axis to different locations, however I would like to run it while I am away, and come back to it being completed its pathing.

The motion I am looking for would be something like the following:
Move x-axis 100mm
Dwell for 4 seconds to allow the sensor to take an auto reading
Move x-axis 100mm and dwell again, continue this and then after a few readings move the Y-axis to the next row and repeat.

I would love to know how to command pathings of this nature, please point me to any resources that may be of assistance.

Thanks in advance for your time.