I'm trying to automate word to replace text in a word document using Python. (I'm on word 2003 if that matters and Python 2.4)

The first part of my replace method below works on everything except text in text boxes. The text just doesn't get selected. I notice when I go into Word manually and hit ctrl-A all of the text gets selected except for the text box.

Here's my code so far:

class Word:
    def __init__(self,visible=0,screenupdating=0):
        pythoncom.CoInitialize()
        self.app=gencache.EnsureDispatch(WORD)
        self.app.Visible = visible
        self.app.DisplayAlerts = 0
        self.app.ScreenUpdating = screenupdating
        print 'Starting word'
    def open(self,doc):
        self.opendoc=os.path.basename(doc)
        self.app.Documents.Open(FileName=doc)
    def replace(self,source,target):
        if target=='':target=' '
        alltext=self.app.Documents(self.opendoc).Range(Start=0,End=self.app.Documents(self.opendoc).Characters.Count) #select all
        alltext.Find.Text = source
        alltext.Find.Replacement.Text = target
        alltext.Find.Execute(Replace=1,Forward=True)
        #Special handling to do replace in text boxes
        #http://word.tips.net/Pages/T003879_Updating_a_Field_in_a_Text_Box.html
        for shp in self.app.Documents(self.opendoc).Shapes:
            if shp.TextFrame.HasText:
                shp.TextFrame.TextRange.Find.Text = source
                shp.TextFrame.TextRange.Find.Replacement.Text = target
                shp.TextFrame.TextRange.Find.Execute(Replace=1,Forward=True)

#My Usage
word=Word(visible=1,screenupdating=1)
word.open(r'C:\Invoice Automation\testTB.doc')
word.replace('[PGN]','1')

The for shp in self.app .. section is my attempt to hit the text boxes. It seems to find the text box, but it doesn't replace anything.