Update Sharepoint List Items

I have a small snippet of code that attaches to a Sharepoint list and loads a sharepoint list using webservices.

Dim listService As New WebReference.Lists()
Dim xmlDoc As New System.Xml.XmlDocument()
     
listService.Credentials = System.Net.CredentialCache.DefaultCredentials
listService.Url = "http://172.16.5.190/EPMI/_vti_bin/Lists.asmx"
Dim ndListView As System.Xml.XmlNode = listService.GetListAndView("Variance Approval Checklist", "")


I can pull the innerXML/outerXML  so I know I am reading the list, but I need help looping through each of the list items and updating several fields of each of the items. I understand I need to make a XML batch job, but I need to iterate through the items and get the IDs of each item. Looking for some example code on the iteration and updating the items.

Thanks