The following works for me:
001 tell application "QuarkXPress Passport 6.x"
002 activate
003 set DocName to name of document 1
004 tell document DocName
005 tell me to doMenu_QX("File", "Save Page as EPS...", "")
006 end tell
007 end tell
008 on doMenu_QX(This_Menu, First_Level, Second_Level)
009 tell application "QuarkXPress Passport 6.x"
010 try
011 if Second_Level is "" then
012 select menu item First_Level of menu This_Menu
013 else
014 select menu item Second_Level of menu item First_Level of menu This_Menu
015 end if
016 on error errMsg number errNum
017 display dialog ("An error " & errNum & " has occured" & return & return & errMsg) with icon stop
018 end try
019 end tell
020 end doMenu_QX
Notes:
• The line numbers included with this script are there to aid future discussions. In order to use this script, you will have to strip all of them.
The problem I see with your command is that the "Export" menu has submenus of its own ("HTML..." and "Layout as PDF...") which for some reason do not appear in the dictionary structure.
HTH