I don’t know about Applescript but I did this by setting up a trigger in Quicksilver.
If you have Quicksilver here’s how I did it as it took a bit of copying and pasting:
First, make sure you have the Services plug-in installed.
Open a document and select some text.
Use Cmd-Esc (you may have to enable this trigger in QS’s prefs) to send the selection to QS.
Tab into the next pane and type View and the ‘View in Tofu’ service should pop up. Hit Cmd-C.
Hit Cmd-, for QS’s prefs.
Go to Triggers --> Custom Triggers and press the + at the bottom to add a new trigger.
The text you had just selected and View in Tofu action should have dropped down when you created the new trigger. In the first pane of the trigger window type in: Curren (the Current Selection proxy object should pop up) if not, then type Proxy and right arrow into the list and select Current Selection proxy object.
Tab into the next pane and hit Cmd-V, the View in Tofu service should have appeared.
Assign a handy dandy key combo and limit the scope of the trigger to DT and you’re done.
I know that probably looks complex but it’s really not as painful as it looks.
Edit: Then again, can’t you assign key-combo’s to Services in the Keyboard pref pane?