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

strPrompt = "Wählen Sie die Zellen aus, die Sie mit " & _
 "eindeutigen Zufallszahlen füllen möchten."
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