I want random numbers generated without repeating

[Johncobb]

In my worksheet in column CC in C1:C20 I want Excel to ganerate 20 random numbers between 1 and 80 without repeating the same numbers.
At present I have the following formula entered and it works, but after I click F9 some repeated numbers are generated.

=INT(RAND()*(80-1)+1)

How can I change the formula or replace it?
Thank you in advance for your help.
Ragards to all supporters.
John.

 

[erik.van.geit]

Hi, Fin Fang Foom,

the formula is looking to previous numbers to avoid duplicates
so you cannot nest it into another formula

use another column

(I don't think you need this complicated formula for your purpose)

kind regards,
Erik

 

[Fin Fang Foom]

Thank you for the reply erik.van.geit.


I took erik suggestion and used a helper column. This is the best that I came up with.

What I did was I inputed this formula in cell C2 and copied down.

=INDEX($A$2:$A$100,IF($A$2:$A$100<>"",INT(1+26*(RAND()))))

Then I inputed this formula in cell E2 and I copied down.

=LOOKUP(REPT("z",255),CHOOSE({1,2},"",INDEX($C$2:$C$100,MATCH(0,COUNTIF($E$1:E1,$C$2:$C$100),0))))

Both formula are an-array Hold down

Ctrl,Shift,Enter

Thanks everyone.

Werid formulas.xls
	A	B	C	D	E	F
1
2	a		g		g
3	b		b		b
4	c		t		t
5	d		r		r
6	e		i		i
7	f		r		a
8	g		a		lf
9	h		lf
10	i		z
11	j		b
12	k		u
13	lf		g
14	mn		a
15	n		k
16	o		t
17	p		u
18	q		s
19	r		t
20	s
21	t
22	u
23	v
Sheet1