Which version of Word? Word Basic was last used integrally in Word 95. You
should be coding in vba if you are working with a more recent version of
Word.

I take it that your customized footer is stored as an AutoText entry?

Are you trying to delete the entire footer or just the field?

You'll need to cycle through the sectionscollection and the footers
collection for each section.

The following macros reaches fields in the headers/footers for updating or
locking. It tests for the nature of the field. You may be able to adopt it
to select said field and replace it with your custom material.

Sub RefFieldUpdateAllStory()
'   Written by Charles Kyle Kenyon 15 November 2001
'   repaired by Jezebel
'   All Story Field Updater - Ref fields
   Dim oField As Field
   Dim oStory As Range
'    On Error Resume Next
   For Each oStory In ActiveDocument.StoryRanges
   ' This goes into headers and footers as well as the regular document
       Do
           For Each oField In oStory.Fields
               If oField.Type = wdFieldRef Then
                   oField.Update
               End If
           Next oField
           Set oStory = oStory.Next
       Loop Until oStory Is Nothing
   Next oStory
End Sub
Private Sub MergeFieldLockAllStory()
'   Written by Charles Kyle Kenyon 1 April 2005
'
'   All Story Field Locker - Merge fields
   Dim oField As Field
   Dim oStory As Range
'    On Error Resume Next
   For Each oStory In ActiveDocument.StoryRanges
   ' This goes into headers and footers as well as the regular document
       Do
           For Each oField In oStory.Fields
               If oField.Type = wdFieldMergeField Then
                   oField.Lock
               End If
           Next oField
           Set oStory = oStory.Next
       Loop Until oStory Is Nothing
   Next oStory
End Sub

Private Sub TOCFieldUpdateAllStory()
'   Written by Charles Kyle Kenyon 15 November 2001
'   repaired by Jezebel
'   All Story Field Updater - TOC fields
   Dim oField As Field
   Dim oStory As Range
'    On Error Resume Next
   For Each oStory In ActiveDocument.StoryRanges
   ' This goes into headers and footers as well as the regular document
       Do
           For Each oField In oStory.Fields
               If oField.Type = wdFieldTOC Then
                   oField.Update
               End If
           Next oField
           Set oStory = oStory.Next
       Loop Until oStory Is Nothing
   Next oStory
End Sub
Private Sub TOCFieldUpdate()
'   Written by Charles Kyle Kenyon 27 January 2005
'   Field Updater - TOC fields
   Dim oField As Field
   On Error Resume Next
   For Each oField In ActiveDocument.Fields
       If oField.Type = wdFieldTOC Then
           oField.Update
       End If
   Next oField
End Sub

Hope this helps.