A little unimaginative but Ok.
Btw, you've wasted several lines, I shrunk it for you;
Graphics 640,480,0,2
SetBuffer BackBuffer()
Dim starx(600),stary(600)
For lop=0 To 600
starx(lop)=Rnd(640)
stary(lop)=Rnd(480)
Next
Repeat
Cls
For lop=0 To 600
starx(lop)=starx(lop)+(1+(lop Mod 3))
If starx(lop)>640 Then starx(lop)=0
Color 85*(1+(lop Mod 3)),85*(1+(lop Mod 3)),85*(1+(lop Mod 3))
Plot starx(lop),stary(lop)
Next
Flip
Until KeyDown(1) Or MouseDown(1)