Is there a way to add a text message signature on a Nokia 5100?

Different phones have different options, so you may have an option to add a signature in your text. While you're texting, open up the menu to see if you have this option.

My old motorola slvr had it... my new bberry does not. I am now a sad loner.

I've looked everywhere, I can't find it. I'm wondering if there isn't an option, if there is a way to tweak it so that I can...