I'm using Microsoft Visual Basic 6.3

I'm not sure if this is the right place to ask this question, but here it goes.

I'm going to make a small Word application which can manipulate a XML file

Code:
Private Sub ManipulateXLM()

Dim doc As MSXML2.DOMDocument
doc.Load ("C:\Documents and Settings\z3xld\Desktop\2Usecases.xml")

End Sub
It says:
runtime error '91':
Object variable or With block variable not set
Can anyone see what might be the problem?