Sub UniqueRandomNumbers()
Dim rngCell As Range, rngCheckRange As Range, rngRangeObject As Range
Dim intTemp As Integer, intCellCount As Integer
Dim strPrompt As String

 strPrompt = "Select the cells you want to fill with unique random values."
 Set rngCheckRange = Application.InputBox(Prompt:=strPrompt, Type:=8)
 
 intCellCount = rngCheckRange.Cells.Count
 
 MsgBox (intCellCount)

 rngCheckRange.ClearContents
 
 For Each rngCell In rngCheckRange
 intTemp = Int(intCellCount * Rnd) + 1
 Set rngRangeObject = rngCheckRange.Find(intTemp, lookat:=xlWhole)
 While Not rngRangeObject Is Nothing
 intTemp = Int(intCellCount * Rnd) + 1
 Set rngRangeObject = rngCheckRange.Find(intTemp, lookat:=xlWhole)
 Wend
 rngCell.Value = intTemp
 Next rngCell
 
End Sub