Setting Numbers In Array And For Loops

What I'm trying to do is: Set numbers (0-51, a deck of cards) in an array like card(0) = 23 (Which would represent, say, the Jack of Clubs). Then card(1) = 35. Now I have two arrays.

The first array is what I have mentioned above.
The second array is holding a Boolean value. So what I do is make a loop going through the card() array from 0-51. In this loop it generates a random number between 0 and 51. Then I check the second array (iCardUsed()) to see if it holds the random number.

So iRndNum = 13 (Say 13 was the random number)
loops through the second array checking if the there is a value of 13. If there isn't then I want it to set card(whatever it was on, say 12) = 13. then make iCardUsed(13) = true saying card 13 was true. I'm not too sure what to do if it was true, not false.

Alright, now that I explained what I was trying to accomplish, I'll post some code and the project.
Public Class Form1
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim iCard(0 To 51) As Integer
Dim iCardUsed(0 To 51) As Boolean
Dim iValue As Integer
[Code] .....

Now, this works, but there are some duplicates in the array. I'm not sure why there would be duplicates. It worked fine when I manually entered data so the logic of it is right. [URL].