Find the proper font, turn proportionate spacing off, and use one of AE's text animation presets to do the character-by-character typing. Make a character-sized solid over the character currently being typed on, and use a blend mode to invert the text color. Then animate the solid to move with hold keyframes.
Add a little glow and you're done!
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA