Need help updating xml fields

Hello

I am new to k2 and i have a schema wich contains mutiple nodes and fields.

i am creating a plan page and i need to update an xml field of the schema process.

my code as follows:

  Dim conk2 As New K2ROM.Connection
        Dim strCon As String
        strCon = "[;];Authentication=Windows;Domain=;User=administrator;Password=password"      

        conk2.Open("ntxgdsbiztalk", strCon)

        Dim callisp As K2ROM.ProcessInstance
        callisp = conk2.CreateProcessInstance("DSLWorkflowsProcess DSL OrderEscalationsEscalations_CallISP")
callisp.XmlFields(           

conk2.StartProcessInstance(callisp)

         

 In the callisp.XmlFields it is asking for the index as integer

How can i update an xml field in a given schema

Thanks a lot