dataview.rowfilter using relations

I have a dataset with 3 tables -- 2 Parent tables and 1 table that is a child
table of both the parents. I create a dataview on the child table and set
the rowfilter to a value which filters the child based on values in both
parent tables. When I edit the parent tables the edit is not reflected in
the dataview.count property. How can I force the dataview to refresh
following parent table edits?

For example:

Parent1
Parent1ID Included Selected
1 0 0
2 0 0

Parent2
Parent2ID Included Selected
1 0 0
2 0 0

Child
ParentID1 ParentID2 Value
1 1 foo1
1 2 foo2
2 1 foo3
2 2 foo4

dv = new dataview(child)
dv.rowfilter="Parent(Parent1Child).Included = True AND
Parent(Parent1Child).Selected = True AND Parent(Parent2Child).Included = True
AND Parent(Parent2Child).Selected = True)"
dv.count = 0

I edit Parent1 so that Parent1ID 1 is both in included and selected and
Parent2 so that Parent2ID 2 is both included and selected.
dv.count is still 0. Why?
--
Pat