dialog to save word document

(french debutant)
I'm using a word.application and the code :

With Dialogs(wdDialogFileSaveAs)
.Name = namedoc
.Show
End With


the user can choose the name and the location of the word file on the disk.
But, if the document exists, how can i get the dialog box which asks the user if he wants to overwrite this document or not ?

thanks...