Option Explicit
 
Private Const Chaine = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"
 
Function Base10toN(ByVal Valeur As Long, ByVal Base As Long) As String
Dim v As Long, str As String
    If (Base < 2) Or (Base > 36) Then Exit Function
    Do
        v = Valeur Mod Base
        Valeur = Int(Valeur / Base)
        str = Mid(Chaine, 1 + v, 1) & str
    Loop While Valeur > 0
    Base10toN = str
End Function
 
Function BaseNto10(ByVal Valeur As String, ByVal Base As Long) As Long
Dim v As Long, i As Long, j As Long, iVal As Long
    If (Base < 2) Or (Base > 36) Then Exit Function
    For i = Len(Valeur) To 1 Step -1
        v = InStr(1, Chaine, Mid(Valeur, i, 1)) - 1
        If v < 0 Or v >= Base Then Exit Function
        For j = 1 To Len(Valeur) - i
            v = v * Base
        Next
        iVal = iVal + v
    Next i
    BaseNto10 = iVal
End Function