The Value property returns the value of the single active item on the specified column. The Values property returns a safe array with all values of selected / active items in the view, on the specified column. The ValueList property returns the list of values for all selected / active items in the view, on the specified column, separated by comma. 

As Microsoft Access uses DAO, you need to use the View's DataSource property rather than control's DataSource property as in the following sample:

Private Sub CascadeTree1_CreateView(ByVal View As Object)
    With View
        Select Case .Index
            Case 1: ' State or City
                .DataSource = CurrentDb.OpenRecordset("Select * FROM States WHERE CountryCode IN (" & .ParentView.ValueList("CountryCode") & " )")
                .Tag = "State"
                .Key = "StateCode"
                .Name = "StateName"
                If (.Items.ItemCount = 0) Then
                    .DataSource = CurrentDb.OpenRecordset("Select * FROM Cities WHERE CountryCode IN (" & .ParentView.ValueList("CountryCode") & " )")
                    .Tag = "City"
                    .Key = ""
                    .Name = "Name"
                    .ColumnAutoResize = False
                End If
            Case 2: ' City
                .DataSource = CurrentDb.OpenRecordset("Select * FROM Cities WHERE CountryCode IN (" & .ParentView.ParentView.ValueList("CountryCode") & ") AND StateCode IN (" & .ParentView.ValueList("StateCode") & ")")
                .Tag = "City"
                .Key = ""
                .Name = "Name"
        End Select
    End With
End Sub

Private Sub Form_Load()
    With CascadeTree1.DefaultView
	.DataSource = CurrentDb.OpenRecordset("SELECT * FROM Countries")
	.Tag = "Country"
	.Key = "CountryCode"
	.Name = "CountryName"
    End With
End Sub

The sample loads the Countries table into the default view ( view with the index 0 ). Once the user clicks / selects / activates an item, the control creates a new view ( with the index 1, 2 and so on ) and fires the CreateView event. During the CreateView event you can load data from different tables based on the parent's view selection. See the ParentView.ValueList