I send the same letters out to many people, but some figures change within, im getting mor clients nd software?

I have a property tax appeal business, and send the same letters over and over again, only the name changes and the figures within. For exaple one letter will say: Hi Jane, We are pleased to inform you we found evidence to reduce your property taxes. Your home is essed at 123,453 and your neighbor located at 1232 JURY LANE with a similar home is essed much lower at 98,234. Therefore there is evidence to warrant an appeal...... there are several paragraphs that stay the same but the name and the figures within change.... I have been copying and pasting but I am afraid I am going to miss it because it hard for me to find all the sections within the letter that change, the essment levels.. Is there an easy way to do this in office...?