random number but not number ?

I need someone to help me write a function to return the number of random numbers specified, but they all need to be unique, the numbers it returns.

Like what I was thinking was something like:

type rnumber
  field rand1,rand2,rand3,rand4,rand5,rand6
end type

global numbers.rnumber = new rnumber

function MyRand(num_numbers%, min%, max%)
;maximum of 6 random numbers returned, prolly have to
;make a type shown above to return all of them at
;same time.
.not_unique2
if num_numbers = 2
  numbers\rand1 = rand(min,max)
  numbers\rand2 = rand(min,max)
  goto check_unique
endif

.check_unique
if num_numbers = 2 then
  if numbers\rand1 = numbers\rand2 then
    goto not_unique2
  else
    goto unique2
  endif
endif

.unique
if num_numbers = 2 then
  return numbers
endif

end function

;Something like above, with 2,3,4,5,6 different
;random numbers being returned depending on the need.

The reason is, I am randomly placing a few puzzle pieces, and I don't want them to overwrite each others grid positions, so if a certain gridx is already selected, I don't want to pick it again, in the random routine. Same for gridy locations.

Any help would be greatly appreciated. What I have written is kind of obfiscuated and not sure if it will work as designed or not.

Thanks

Learned this from a post by Douglas:

SeedRnd(MilliSecs())
Dim pickarray(11)
For a=0 To 11
	pickarray(a)=a
Next
Dim gridarray(2,3)
c=11
For a=0 To 2
	For b=0 To 3
		d=Rand(0,c)
		gridarray(a,b)=pickarray(d)
		pickarray(d)=pickarray(c)
		c=c-1
	Next
Next
Print gridarray(0,0)+" "+gridarray(0,1)+" "+gridarray(0,2)+" "+gridarray(0,3)
Print gridarray(1,0)+" "+gridarray(1,1)+" "+gridarray(1,2)+" "+gridarray(1,3)
Print gridarray(2,0)+" "+gridarray(2,1)+" "+gridarray(2,2)+" "+gridarray(2,3)
WaitKey()