XML - Write Node Attribute

This custom action lets you write the value of an attribute associated to an XML node.

Property Name	Data Type	Description
AttributeName	string	A string specifying the name of the attribute to create or change.
AttributeValue	string	Value of the attribute you want to set. You can use variables such as %DESTPATH%.
IDXML	TXMLID	A unique string identifier associated to the opened XML resource you want to write data to.
PathToNode	XPath	XPath expression to the node that contains the attribute.

Use of XPath is explained at http://msdn.microsoft.com/en-us/library/ms256086.aspx