Notes/Domino 6 and 7 Forum : Date item, multiple values of NotesDateRange and NotesDateTime

I have two date fields on a form (startdate and enddate). Now I'm trying to populate a third date field with multiple values from that fields. The new entry can be a daterange or a single value (if startdate and enddate are the same). My problem is the syntax to get the new value into the existing array.

Dim ws As New NotesUIWorkspace
Dim session As New NotesSession
Dim uidoc As NotesUIDocument
Dim doc As NotesDocument
Dim dtStart As NotesDateTime
Dim dtEnd As NotesDateTime
Dim item As NotesItem
Dim values As Variant
Dim dateRange As NotesDateRange

Set uidoc = ws.CurrentDocument
Set doc = uidoc.Document

Set dtStart = New NotesDateTime(doc.getitemvalue("StartDate")(0))
If (doc.getitemvalue("EndDate")(0)<>"") Then
Set dtEnd = New NotesDateTime(doc.getitemvalue("EndDate")(0))
Else
Set dtEnd = dtStart
End If

Set dateRange = session.CreateDateRange()
Set dateRange.StartDateTime = dtStart
Set dateRange.EndDateTime = dtEnd

Set item = doc.GetFirstItem("Ferien_Daten")
If Not item Is Nothing Then
values = item.GetValueDateTimeArray()
End If

Dim ub As Integer
ub = Ubound(values)

Redim Preserve values(ub+1)
Set values(ub+1) = dateRange

doc.Ferien_Daten = values
Call uidoc.Refresh

So I use the new "GetValueDateTimeArray". The problem is if there's even one "single value" thats no daterange, the type of the values-array is notesdatetime and I get a type mismatch error with "Set values(ub+1) = dateRange". If there are only dateranges in the field the type of values is notesdaterange and it works. If I save the date field it shrinks a daterange with a single value to a datetime. So I get the error next time I try to populate the field. Has anybody an idea about that?