PSP/AS-Animated Text Question

I'm trying to make an icon that looks like it's being 'typed' as you look at it, where each new letter appears on a new frame.

My problem is, I'm not sure if I'm supposed to do each frame in a layer or a bajilian images for each new letter. Maybe I'm just tired and my brain doesn't want to think on it. Any advice?

(ack, posted to the wrong comm originally *slaps self* I should not be making icons while this stupid*