xforms:send and receive XML data

[arti]

Hi all.

I have a problem/question with XForms.
I have 2 instnace in my document, instance1 and instance2.

<xforms:instance xmlns="" id=instance1">
....
</xforms:instance>

<xforms:instance xmlns="" id=instance2">
....
</xforms:instance>

Where is no problem to send and receive data from/to instance1 or instance2
singly. For example:

<xforms:submission id="submit1" action="http://localhost/test1.php"
id="submit1" method="post" replace="instance" ref="instance('instance1')/>
<xforms:submission id="submit2" action="http://localhost/test2.php"
id="submit1" method="post" replace="instance" ref="instance('instance2')/>

Here is a path:
instance in my document -> XML document -> service -> XML document ->
instance in my document

But I want send data from instance1 to my php service and receive it to
instance2:

instance1 in my document -> XML document -> service -> XML document ->
instance2 in my document

Do you know how resolve it, is it possible?
Thank You in advance for your help.

Arti