Creating dust at random points in a line between two positions

I've been able to create dust vortexes, dust rings, dust ovals, and many other effects with dust, but this one has me stumped.

I need to spawn dust between two projectiles at random points between them in a line. Projectile one spawns projectile two. I've passed in the parent projectile's whoAmI through NewProjectile's ai[1] (ai[0] is occupied). I then store that info using Projectile parentProj = Main.projectile[(int)projectile.ai[1]].

I'm only...

Creating dust at random points in a line between two positions