Så fandt jeg ud af det
Sub RndTaliRng()
Dim MyRng As Range
Dim intCells As Integer
Dim arrRng() As Integer
Dim i As Integer
With ThisWorkbook.Worksheets("Ark1")
Set MyRng = Range(.Range("A1"), .Range("B20"))
intCells = ThisWorkbook.Worksheets("Ark1").Range(.Range("A1"), .Range("B20")).Cells.Count
ReDim arrRng(intCells)
For i = 1 To UBound(arrRng)
arrRng(i) = ThisWorkbook.Worksheets("Ark1").Cells(1, i)
Next i
For i = 1 To UBound(arrRng)
Randomize
MyRng(i).Value = Int((100 - 2 + 1) * Rnd + 1)
Next i
End With
End Sub