selection

Sub SelectLignePaires()
Dim plage As Range, r As Range
For Each r In ActiveSheet.UsedRange.Rows
    If r.Row Mod 2 = 0 Then
        If plage Is Nothing Then
            Set plage = r
        Else
            Set plage = Union(plage, r)
        End If
    End If
Next
If Not plage Is Nothing Then plage.Select
End Sub

Sub SelectionLignes()
Dim plage As Range, r As Range
Dim Incr As Integer
Incr = InputBox("Valeur du pas de lignes ", "Sélectionner une ligne sur n")
If Val(Incr) < 0 Or Val(Incr) > 20 Then Exit Sub
For Each r In ActiveSheet.UsedRange.Rows
    If r.Row Mod Incr = 0 Then
        If plage Is Nothing Then
            Set plage = r
        Else
            Set plage = Union(plage, r)
        End If
    End If
Next
If Not plage Is Nothing Then plage.Select
End Sub