So here's my function, could anyone tell me if this is trustable...or
better: if it can be done easier?
(it runs through the whole year comparing the values!?!?! ...and then
conects both dates in a string like "dd-mm-yyyy untill dd-mm-yyyy")

Public Function WeekDatum(intW As Integer) As String
Dim intWeek As Integer
Dim Datum As Date
Dim N As Integer
    For N = 1 To DateDiff("d", DateSerial(Year(Now), 1, 1),
DateSerial(Year(Now), 12, 31)) + 1
        Datum = DateAdd("d", N, DateSerial(Year(Now) - 1, 12, 31))
        intWeek = Format(Datum, "ww", vbMonday)
        If intWeek = intW Then
            WeekDatum = Format(Datum, "ddd, dd-mmm-yyyy")
            Exit For 'Got the 1st so get out the for
        End If
    Next N
    Datum = DateAdd("d", 6, Datum) 'Add 6 days to get the last date
    WeekDatum = WeekDatum & " t/m " & Format(Datum, "ddd, dd-mmm-yyyy")
End Function

I tried this too but didn't work allways (week 53???)

=================================================
Public Function ExtractDate(iWeekday As Integer, iWeek As Integer, iYear As
Integer) As Date
Dim Result As Date
    'To check the date of the first weekday in the first week of the year
    'start looking from one week before the beginning of the year
    Result = DateSerial(iYear - 1, 12, 25)

    'Check if the next date is in week 1
    'otherwise continue the loop
    Do
        Result = Result + 1
    Loop Until DatePart("ww", Result, vbUseSystemDayOfWeek, vbUseSystem) = 1

    'Add the weeks and days to the found date
    ExtractDate = DateAdd("ww", (iWeek - 1), Result) + (iWeekday - 1)
End Function
=================================================

Hope this helps,
Johan.