I don't understand what you mean by 'grouping'.
The error message you're reporting suggests you've applied some form of protection to the document. Note that, unless you're actually trying to prevent editing somewhere, you don't need protection with content controls. If you do want protection, you'll need to add some content controls to the 'age' cells and the code will need a minor modification to send its output to those contents controls - the two references to:
Code:
.Paragraphs.Last.Range.Text =
will need to be changed to:
Code:
.Paragraphs.Last.Range.ContentControls(1).Range.Text =