Changing the format on the last line of text in a text box

Hi all, 

I'm asking something that probably has a very simple and obvious answer, but I just can't seem to find it.... I am creating a book full of hundreds of personal messages. My client has now asked for the names to be in bold. Currently the names are on a separate last line of each text box (so almost like a new paragraph I guess), and I want to change them to a specific font and put them in bold. Is there a simple way to do this? I've tried paragraph formatting but it tends to change the first line as well. Bonus points if there is a way to do it without also making the xxx's that some people have added change too.  Text below is an example of current formatting:

Dear Person answering this,

Thanks so much for being brilliant and taking the time to respond and help me out with this. I really appreciate it.

Katie and occasionally people have added an x or two

And the way I'd like it too look:

Dear Person answering this,

Thanks so much for being brilliant and taking the time to respond and help me out with this. I really appreciate it.

Katie and occasionally people have added an x or two

Please let there be a quick way to do this, rather than manually going through and changing them all!

Thanks!