... crea semplicemente il tuo albero su cui poi andrai a lavorare 
codice:
Public Doc As New MSXML2.DOMDocument30
Public xml As IXMLDOMElement
Public Itinerari As IXMLDOMElement
Public Vehicle As IXMLDOMElement
Public dia As IXMLDOMElement
Public Pesada As IXMLDOMElement
Public Element As IXMLDOMElement
Public Percial As IXMLDOMElement
Public Percentatge As IXMLDOMElement
Public Data As IXMLDOMElement
Public Hora As IXMLDOMElement
Function CreaXML()
Set xml = Doc.createNode(NODE_ELEMENT, "PESADES_PARCIALS", "")
Set Itinerari = Doc.createNode(NODE_ELEMENT, "ID_ITINERARI", "")
Set Vehicle = Doc.createNode(NODE_ELEMENT, "ID_VEHICLE", "")
Set dia = Doc.createNode(NODE_ELEMENT, "DIA", "")
Set Pesada = Doc.createNode(NODE_ELEMENT, "PESADA", "")
Set Element = Doc.createNode(NODE_ELEMENT, "ID_ELEMENT", "")
Set Percial = Doc.createNode(NODE_ELEMENT, "PES_PARCIAL", "")
Set Percentatge = Doc.createNode(NODE_ELEMENT, "PERCENTATGE_OMPLERT", "")
Set Data = Doc.createNode(NODE_ELEMENT, "DIA", "")
Set Hora = Doc.createNode(NODE_ELEMENT, "HORA", "")
Doc.appendChild xml
xml.appendChild Itinerari
xml.appendChild Vehicle
xml.appendChild dia
xml.appendChild Pesada
Pesada.appendChild Element
Pesada.appendChild Percial
Pesada.appendChild Percentatge
Pesada.appendChild Data
Pesada.appendChild Hora
CreaXML = Doc.xml
MsgBox CreaXML
End Function
Private Sub Form_Load()
Call CreaXML
Unload Me
End Sub
P.s. assicurati di avere referenziato la libreria giusta
Io uso il vb6 e come libreria ho referenziato la "micosoft XML,v3.0"