To start with 1000, you need to make two changes. The first change is in
what the macro does when it hasn't been used before. Change the 1 to 1000
here:
If Order = "" Then
Order = 1000 ' <====
Else
Order = Order + 1
End If
After you make this change, delete the file C:\Settings.Txt if it exists, so
the sequence will start over.
The second change concerns the formatting of the numbers. The macro as-is
only allows for three-digit numbers, but you need four digits. Change the
two lines near the end to have three zeros before the # sign:
ActiveDocument.Bookmarks("Order").Range.InsertBefore Format(Order, "000#")
ActiveDocument.SaveAs FileName:="path" & Format(Order, "000#")