To do this with document properties --

1. Define a custom document property for each item of data you need to deal
with, using File > Properties > Custom. Insert a dummy value in each case.
If you define the properties in a template they are inherited by docouments
created from the template.

2. In place of the bookmarks in your document, insert DocProperty fields.

3. In your code, instead of setting the value of the bookmark, set the value
of the property --

ActiveDocument.CustomDocumentProperties("Property Name").Value = ....

4. When you've set all the property values, update the fields.