The code uses the source template to create the new document and the
Code:
oDoc.Range.Text = ""
line ensures that the text in that document is removed first. The remaining bookmarks are added at the end of the document.
If you need Chapter 1 and Chapter 2 to be included always, the simplest approach is to check the two check boxes and change their properties to check the option 'Contents cannot be edited'. Then they cannot be changed from the template.
The lines
Code:
Else
MsgBox "No checkboxes were checked"
are then superfluous.