XML: How to change attribute name value by concatenating attribute value from the same node and attribute value from the parent node, using VBScript?

I have part of xml code like this:

<datasource caption='CAPTION_NAME' inline='true' name='xxx'>
  <connection authentication='def' class='abc' schema='SCHEMA' server-oauth='' workgroup-auth-mode='prompt'>
    <relation name='CAPTION_NAME' table='[SCHEMA].[CAPTION_NAME]' type='table' />

I want to change value of attribute name "table" in node "relation" using VBScript. This value should be changed by using attribute value of "name" in "relation" node and attribute value of "schema" in "connection" node.

Can somebebody help me with this? I tried to use setAttribute or document.write but it didint worked well.

TNX IN ADVANCE!