Generate random numbers without math.randomseed?

Here below is the script. I have a 8 blocks in Workspace, which have the same identical script. I cannot use math.randomseed(tick(), or math.randomseed in general, because that would affect every single block. Basically, if math.randomseed generates the number 4, all the other blocks will have 4.

Without math.randomseed, the blocks generate as different things, but don't change when you rejoin the server.

Any way I can fix this?

m=math.random(1,1000)
if m > 999 and m < 1001 then
	k=Instance.new("Sparkles")
	script.Parent.BrickColor=BrickColor.new("Black")
	script.Parent.Material="Cobblestone"
	script.Parent.BlockValue="Black Iron"
	k.Color=Color3.new(85,0,255)


elseif m > 995 and m < 999 then
	g=Instance.new("PointLight")
	h=Instance.new("Fire")
	script.Parent.BrickColor=BrickColor.new("Dark blue")
	script.Parent.Material="Foil"
	script.Parent.BlockValue="Bluesteel"
	g.Parent=script.Parent
	g.Brightness=5
	g.Color=Color3.new(0,0,255)
	g.Range=10
	h.Parent=script.Parent
	h.Heat=3
	h.Color=Color3.new(0,0,255)
	h.SecondaryColor=Color3.new(0,0,255)
	h.Size=13

elseif m > 990 and m < 995 then
	a=Instance.new("PointLight")
	script.Parent.BrickColor=BrickColor.new("Forest green")
	script.Parent.Material="Pebble"
	script.Parent.BlockValue="Viridian"
	a.Parent=script.Parent
	a.Brightness=5
	a.Color=Color3.new(85,170,0)
	a.Range=10

elseif m > 985 and m < 990 then
	t=Instance.new("PointLight")
	script.Parent.BrickColor=BrickColor.new("Really red")
	script.Parent.Material="Cobblestone"
	script.Parent.BlockValue="Adurite"
	t.Parent=script.Parent
	t.Brightness=5
	t.Color=Color3.new(255,0,0)
	t.Range=10
elseif m > 975 and m < 985 then
	script.Parent.BrickColor=BrickColor.new("Eggplant")
	script.Parent.Material="Granite"
	script.Parent.BlockValue="Obsidian"

elseif m > 950 and m < 975 then
	script.Parent.BrickColor=BrickColor.new("Pastel Blue")
	script.Parent.Material="Ice"
	script.Parent.BlockValue="Diamond"

elseif m > 900 and m < 950 then
	script.Parent.BrickColor=BrickColor.new("New Yeller")
	script.Parent.Material="Ice"
	script.Parent.BlockValue="Gold"

elseif m > 750 and m < 900 then
	script.Parent.BrickColor=BrickColor.new("CGA brown")
	script.Parent.Material="Slate"
	script.Parent.BlockValue="Iron"

elseif m > 600 and m < 750 then
	script.Parent.BrickColor=BrickColor.new("Institutional white")
	script.Parent.Material="Ice"
	script.Parent.BlockValue="Silver"
elseif m > 400 and m < 600 then
	script.Parent.BrickColor=BrickColor.new("Rust")
	script.Parent.Material="Ice"
	script.Parent.BlockValue="Copper"

elseif m > 0 and m < 400 then
	script.Parent.BrickColor=BrickColor.new("Dirt brown")
	script.Parent.Material="Concrete"
	script.Parent.BlockValue="Dirt"
end