Export a specific calendar from iCal

Hi,
I'm new to AppleScript (and must say I find it very frustrating...). I'm 
trying to export a specific calendar from iCal, so got the following:
tell application "iCal" to activate
tell application "System Events" to tell process "iCal"
   tell menu item "ExporterŠ" of menu "Fichier" of menu bar 1 to click
   tell sheet 1 of window 1
      delay 1
      keystroke "d" using command down -- select desktop
      tell button "Exporter" to click
      delay 1
   end tell
end tell
Now this export the currently selected calendar but I want to export 
calendar "C". Can't find a command like
   select calendar "C"
How do I do that?  Thanks for the help
-- 
Francois