Install instructions:
Unzip the archive and place the contents in the Scripts folder located within the Adobe After Effects CS3 Support Files folder. Run After Effects and go to General Preferences, and toggle the "Allow Scripts to Write Files and Access Network".
Run the script from File>Scripts>KeyEd Up.jsx
After updating the shortcuts, restart AE for the changes to take effect - since this is not a part of AE, but only a script.
KeyEd_Up.zip 20.61Kb - Downloads: 83
KeyEd_Up_CS4.zip 21.01Kb - Downloads: 89

Additional extension information
More info: Adobe After Effects Exchange