Estrazione casuale righe tabella excel

Sub CasualiUnivoci() '<<<<<<<<<< da eseguire
Dim N As Long, Ur As Long, Rand As Long, i As Long, UrTo As Integer, k As Worksheet
Set wk = Worksheets("ElencoRighe")
wk.Cells.ClearContents
c = 1
For j = 1 To Sheets.Count
    UrTo = 0
    If Sheets(j).Name <> "ElencoRighe" Then
        'ipotizzando che la col. A di ciascun foglio possa essere presa _
         per il conteggio massimo delle righe del foglio :
        Ur = Sheets(j).Range("A" & Rows.Count).End(xlUp).Row
        If Ur > 100 Then UrTo = 100 Else UrTo = Ur
        If Ur > 1 Then
            ReDim Unique(1 To Ur, 1 To 1)
            For i = 1 To Ur
                Randomize
                Do
                    Rand = Int(Ur * Rnd) + 1 'nota: + 1 per evitare che esca la riga 0 (zero)
                    If IsUnique(Rand, Unique) Then Unique(i, 1) = Rand:  Exit Do
                Loop
            Next
        End If
    End If
    If Sheets(j).Name <> "ElencoRighe" Then
        wk.Cells(1, c) = Sheets(j).Name
        For i = 1 To UrTo
            Cells(i + 1, c) = Unique(i, 1)
        Next i
        c = c + 1
    End If
Next j
End Sub

Function IsUnique(Num As Long, Data As Variant) As Boolean
Dim iFind As Long
On Error GoTo Unico
iFind = Application.WorksheetFunction.Match(Num, Data, 0)
If iFind > 0 Then IsUnique = False: Exit Function
Unico:
IsUnique = True
End Function