MS WORD PLUGIN (AUTO LETTER WRITER)

Attached Document has Parts like " PATIENT HISTORY" and under it sub options. There are many several main parts like Patient History with their respective sub sections. What i need is a word plugin that will be menu based and also side like when you do mail merge on Ms Word. Option to select then Main Categories and once main category is selected there would be all the subs which i can click on and it will put the contents of the sub category on the document. This way i can build a letter buy clicking main category and selecting the sub category(phrases) and building the letter this way.