See:

• Repeating Data Using Document Properties Content Controls and Other Mapped Content Controls
• Mapped Content Controls by Greg Maxey, MVP
• Repeating Data (Populating Multiple Like Fields) by Greg Maxey, MVP

If you can add Add-Ins to your system, I strongly recommend using Greg Maxey's free utility Custom Content Control Insert Dialog. It makes mapped content controls the optional default and has other nice features. Once you install it, it is even easier than the Document Property Content Controls and much more flexible.