Public Function Datum_KW(ByVal KW As Integer, _
  ByVal Year As Integer, Tag_Name As String) As Date
 
  On Error GoTo Err_Datum_KW
 
  Dim lday As Long
  Dim vDate  As Date
 
  vDate = "01.01." & CStr(Year)
  For lday = 0 To 6
    If Format(vDate + lday, "ww", vbMonday, vbFirstFullWeek) = 1 Then
      Datum_KW = vDate + lday + (KW - 1) * 7 - 2
      Datum_KW = Datum_KW - (Weekday(Datum_KW, Tag_Name) - 1)
    End If
  Next lday
  Exit Function
 
Err_Datum_KW:
  MsgBox Err.Description
End Function