External Automation using VB.NET to Infopath

[Jeff]

Could you help me? I need to create a solution the externally automates
InfoPath using VB.NET.

Right now I'm able to open the form:
Private xDoc As InfoPath.XDocument
xDoc = xDocApp.XDocuments.NewFromSolution("...")

But, how do I get/set the values of the nodes?
Dim objXMLNode As XmlNode
objXMLNode = xDoc.DOM.selectSingleNode("//myFields") ' This Fails


Thanks,

Jeff