replace text in FolderItem names recursively

Hello,
I am trying to replace all occurence of oldtext within a specified
FolderItem's name and its subcontents' names. I wrote a sub to do this
in RB2007r1:

sub RenameFolder(folder as FolderItem, oldtext as string, newtext as
string)
  Dim i as Integer

  If folder.directory then
    folder.name=replaceAll(folder.name, oldtext, newtext)
    if folder.count > 0 then
      For i=1 to folder.count
        If folder.TrueItem(i).directory then
          RenameFolder folder.TrueItem(i), oldtext, newtext
        else
          folder.TrueItem(i).name=replaceAll(folder.TrueItem(i).name,
oldtext, newtext)
        end if
      next
    end if
  else
    folder.name=replaceAll(folder.name, oldtext, newtext)
  end if
end sub

But it sometimes works, sometimes does not. I think it's because the
item index numbers within a folder change when one of its' subcontents
is renamed. What can I do about it?

Thanks