Dependent drop down

[Brian]

I have a dependent drop-downs/list-box in InfoPath using Filters working in a
repeating table for the first row; however, the subsequent rows contain
previously filtered data.

We have made a repeating table. There is a hierarchy in this table. There
are two drop down boxes Task and SubTask.We have made an XML file as
secondary data source.
<?xml version="1.0" encoding="UTF-8"?>
<TimeSheet>
<Table>
<Row>
<Selection>
<SelectedTask/>
<SelectedSubTask/>
</Selection>
</Row>
</Table>
<TaskList>

<Task name="Project">
<SubTask name="Project, Task 1"> </SubTask>
<SubTask name="Project, Task 2"> </SubTask>
<SubTask name="Project, Task 3"> </SubTask>

</Task>

<Task name="Civic duty">
<SubTask name="Civic duty,Civic duty 1"> </SubTask>
<SubTask name="Civic duty,Civic duty 2"> </SubTask>
<SubTask name="Civic duty,Civic duty 3"> </SubTask>
</Task>
</TaskList>
</TimeSheet>


When we fill in the first row of the repeating table, we have no problems.
But when we insert a second item, the subtasks of the first row and the
subtasks of the second row are shown. But we only want the subtasks of the
selected Task of the second row to be shown.

I've already tried to work with a Rule but it failed.

I tried to make changes to the xslt file
and tried following this blog
http://blogs.msdn.com/infopath/archive/2004/09/13/228881.aspx

But it didn't help either.

Help me on this.