OK. I solved it in this way: I wrote a module with two functions, first one
creates a string to be included inside IN expression of WHERE clause, and
second one to synchonize any "child" listbox in correspondence to "parent"
listbox.

Option Compare Database

Function MultiselectListValues(ListFullName As Control) As String
'This function returns a string, as comma-separated list of values,
'based on selected values in a multi-select list box.
'This string can be used inside IN expression in WHERE clause of a query

Dim strWhere As String, varItem As Variant

'Request to edit items selected in the list box
'If no items selected, then nothing to do
If ListFullName.ItemsSelected.Count = 0 Then Exit Function
'Loop through the items selected collection
For Each varItem In ListFullName.ItemsSelected
   'Grab the column for each selected item
   strWhere = strWhere & "'" & ListFullName.Column(0, varItem) & "'" & ","
Next varItem
'Throw away the extra comma on the "IN" string
strWhere = Left$(strWhere, Len(strWhere) - 1)
'Finish creation of "IN" string
MultiselectListValues = strWhere

End Function

Function SynchronizeListBox(ParentListFullName As Control, ChildListFullName
As Control, SelectExpression As String, LinkField As String)
'This function synchronize recordset in child list box, based on selectde
values in parent list box.
'Parent list box has a query or SQL statement as its rowsource, while
recordset of child list box is created programmatically.

Dim db As Object
Dim qdf As Object
Dim qdfSQL As String
Dim rs As Object
Dim strWho As String
Dim strWhere As String
Dim strSQL As String

DoCmd.Hourglass True

   Set db = CurrentDb

strWho = LinkField
strWhere = MultiselectListValues(ParentListFullName)

Set qdf = db.CreateQueryDef("")
If strWhere <> "" Then
   strSQL = SelectExpression & " WHERE (((" & strWho & ")IN(" & strWhere &
")));"
Else
   strSQL = "select plants.plant from plants WHERE " & strWho & "=""""" &
";"
End If
   qdf.SQL = strSQL
   qdf.returnsrecords = True
Set rs = qdf.openrecordset()

Set ChildListFullName.Recordset = rs.clone

rs.Close
qdf.Close

DoCmd.Hourglass False

End Function

"Allen Browne" <AllenBrowne@SeeSig.Invalid> je napisao u poruci interesnoj
grupi:43cd1af6$0$23585$5a62ac22@per-qv1-newsreader-01.iinet.net.au...