Laser.h: Pause the queue with Block.h is_g123 bool

I am currently a Mechanical Engineering student at the University of Idaho and am working with a Smoothie board to interface a MIG welder to a 3D gantry system. To simplify the G-code for future users, I have successfully used a similar process to laser.h; therefore, no custom M commands are needed. The problem is when the is_g123 bool is received, I would like for the gas flow to turn on and dwell for 1 second before the steppers start moving to their target positions. Is there a way to halt the queue and resume it so these actions can take place before movement occurs?

Imported from wikidot