Amending the Dialogue.tlk through scripting

I'm not a very good scripter, but I have five spells, each with a .wav. I want the .wav to play whenever I cast the spell, but NOT when anyone else casts the spell.

So, I want to amend the dialogue.tlk to do it. Although I could simply use an TBG tool, I want to play with this character on multiplayer, so he should be able to add strings to ANY dialogue.tlk.

How do I add strings through scripting, for say, spells (A),(B),©,(D),(E),(F), using Magic Missile, Melf's Acid Arrow, Fireball, Greater Malision, and Cloudkill, respectively?

Err...sorry. I want to add the white-bulging circle beneath the characters to simulate speaking, as opposed to simply playing a .wav during the casting of a spell.