Originally posted by: rootaxs
Here's how to do in in Ultradev at least.
Edit > Keyboard Shortcuts
Choose "Macromedia Standard" for the current set and duplicate it (Button right next to it). Name this set whatever you want.
Go to the "Menu Commands" dropdown. Then Text > Style > Underline. Hightlight "Underline" and use whatever shortcut you want - CTRL+9 is usually not taken.
Click OK and you're all set. 🙂