You wouldn't necessarily need change the end-block only, you could make an invisible damageless bullet that each step does something like this:
xx = x /10
yy = y/10
if xx != xp or yy != yp {
t[xx,yy] = v*
v = t[xx,yy]
t[xx,yy] = 1
}
xp = xx
yp = yy
//apply constants
But that would yield a...