Calculate Age From Content Controls

[kintap]

I have searched and found many references, but it is beyond my skill to get this to work with content controls

Previously my form was made with form fields and I was able to do the age calculations. However, we have moved towards content controls to allow better spell checking and text formatting.

Attached is partially converted form (the file extension needs to be renamed to .dotm, changed it to .zip in order to upload), any help is great. I am really stumped.