Can not update List Box Selected Collection in code - vba

Question

I have a list box on a form being populated from a query, with items selected on basis of matching a delimited list. So sSystemString equals something like "A;B;C"
Then I load records A,B,C,D,E,F from the SQL Server DB and only A,B,C should be selected.
Is there a native way to do this in MS Access (2010). I'm using an ADP in this case.
I'm doing it via code but I can't the selected property does not reflect my changes, nor does the form.
Here's my code:
Dim rs As New ADODB.Recordset
Dim sSystemString As String
If Not IsNull(Me.OpenArgs) Then sSystemString = Me.OpenArgs
' Load this list box with SRC Systems
Call rs.Open("SELECT DISTINCT System FROM dbo.System WHERE System IS NOT NULL", _
CurrentProject.Connection, adOpenForwardOnly, adLockReadOnly)
Do Until rs.EOF
lstSrcSystems.AddItem (rs.Fields(0))
If InStr(sSystemString, rs.Fields(0)) > 0 Then
lstSrcSystems.Selected(lstSrcSystems.ListCount - 1) = True
End If
rs.MoveNext
Loop
My code definitely hits the lstSrcSystems.Selected(lstSrcSystems.ListCount - 1) = True line.
After running this line, inspecting the property in the immediate window still returns 0 (it doesn't change). On the form, the item is also not selected.
UPDATE: I just checked my code again and now it is being updated, but the next AddItem apparently unselects it again.
I suspect I have some weird combination of properties that make this read only, but I can select items interactively, and indeed when I extract the selected items back off in code, the Selected property works as expected - i.e. I select an item on the form and it reflected in this property.
The form is unbound and is called from a button on another form with this code:
DoCmd.OpenForm "fSiteList", acNormal, , , acFormEdit, acDialog, Me.SRCSystems

Answer 1

The problem was actually that lstSrcSystems.AddItem (rs.Fields(0)) was resetting the Selected state. I can't find any mention of this behaviour or how to turn it off. I altered my form as follows:
Form / Data properties all blank (unbound)
List Control / Data / Control Source: blank
List Control / Data / Row Source: SELECT statement populating my list
This has the effect of populating the list but not binding the list or form to anything. (I found that binding it stopped me interactively editing data on it)
Form_Load code behind the form was changed to select already existing items:
Private Sub Form_Load()
Dim sSystemString As String
Dim iIndex As Integer
' List is bound to site list (from connections)
' Highlight those that are listed
If Not IsNull(Me.OpenArgs) Then sSystemString = Me.OpenArgs
iIndex = lstSrcSystems.ListCount
Do While iIndex > 0
If InStr(sSystemString, lstSrcSystems.ItemData(iIndex)) > 0 Then
lstSrcSystems.Selected(iIndex) = True
End If
iIndex = iIndex - 1
Loop
End Sub
I'm still curious to know whether there is a more 'built in' way to achieve this: edit a delimited string field.