As far as I know, the only way to do this is with a Seq field:
{ SEQ SeqNameHere \# "0000" }
To insert the field braces, press Ctrl+F9. Then type the code as shown
(except for the SeqNameHere part, where you can choose a name that
makes sense to you) and press F9 to update the display.
You can use copy and paste to insert the number at multiple locations.
Note that Seq fields do not update automatically, which will be
especially apparent if you use copy and paste to insert them. Printing
or previewing should update them, though (it definitely will if you
enable the option to update fields on the Print tab of Tools>Options).
For more about the Seq field, see Word Help.
--
Stefan Blom
Microsoft Word MVP
in message