XL: How to Create Unique Random Integers Between Two Values

ID: Q151470

The information in this article applies to:

SUMMARY

In Microsoft Excel, you can write a macro to create a list of unique random integers between two numbers.

MORE INFORMATION

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   http://www.microsoft.com/support/supportnet/refguide/
The following macro prompts the user for a starting integer and an ending integer, then the macro prompts the user to input the number of random numbers to generate. Next, it lists that number of unique integers on the active worksheet.

To create and run the macro, follow these steps:

1. Type the following code in a module sheet: 

      Option Explicit

      Sub Unique_Numbers()

         Dim x As Long, y As Long, z As Long, tempnum As Long
         Dim flag As Boolean
         Dim i As Integer
         Dim foundCell As Range

         Application.ScreenUpdating = False

         x = Application.InputBox("Enter starting Random Number" _
            , "Random Number Generation", 1, , , , , 1)
         y = Application.InputBox("Enter ending Random Number" _
            , "Random Number Generation", 1000, , , , , 1)
         z = Application.InputBox("How many random numbers would" _
            & "you like to generate (<15000)?" _
                , "Random Number Generation", 100, , , , , 1)
         If z = 0 Then Exit Sub

         If z > 15000 Then z = 15000

         If z > y - x + 1 Then
             MsgBox "You specified more numbers to return than " _
                     & "are possible in the range!"
             Exit Sub
         End If

         Randomize

         Cells(1, 1) =  Int((y - x + 1) * Rnd + x)

         For i = 2 To z
             Do
                 flag = False
                 Randomize
                 tempnum = Int((y - x + 1) * Rnd + x)

                 Set foundCell = Range("a1", _
                        Range("a1").End(xlDown).Address).Find(tempnum)
                 If Not (foundCell Is Nothing) Then
                     flag = True
                 End If

             Loop Until Not flag

             Cells(i, 1) =  tempnum

         Next

      End Sub
2. Open a blank worksheet.

3. On the Tools menu, click Macro. 

   In Microsoft Excel 97, on the Tools menu, point to Macro, and click
   Macros.
4. Click the Unique_Numbers macro, and then click Run.

REFERENCES

For additional information about getting help with Visual Basic for Applications, please see the following article in the Microsoft Knowledge Base: 

   ARTICLE-ID: Q163435
   TITLE     : VBA: Programming Resources for Visual Basic for
               Applications
Additional query words: XL97 
Keywords          : kbprg kbdta kbdtacode PgmHowto KbVBA 
Version           : WINDOWS:5.0,5.0c,7.0,97; MACINTOSH:5.0,5.0a,98
Platform          : MACINTOSH WINDOWS
Issue type        : kbhowto

Last Reviewed: May 18, 1999