AppleScript to Option-click on the Dropbox Menu Bar Icon
Using terms from the (FREE) AppleScript Toolbox scripting addition, this code will handle your question.



The code in this updated answer will automatically get the coordinates of the DROPBOX icon in the status bar...  Whether it's location stays the same or changes



tell application "System Events"
    tell its UI element "Dropbox"
        tell its menu bar 2
            set originalCoordinates to position
        end tell
    end tell
end tell

set itemOne to (item 1 of originalCoordinates) + 10
set itemTwo to (item 2 of originalCoordinates) + 10

set dropboxMouseLocation to {itemOne, itemTwo}
AST set mouse point location dropboxMouseLocation
AST click at dropboxMouseLocation holding modifier key ast option key






UPDATE

This is following version of the code will return the mouse to where its original location was before clicking on the Dropbox status menu icon



set originalMouseLocation to AST mouse point location

tell application "System Events" to tell its UI element "Dropbox"
    tell its menu bar 2
        set originalCoordinates to position
    end tell
end tell

set itemOne to (item 1 of originalCoordinates) + 10
set itemTwo to (item 2 of originalCoordinates) + 10

set dropboxMouseLocation to {itemOne, itemTwo}
AST set mouse point location dropboxMouseLocation
AST click at dropboxMouseLocation holding modifier key ast option key

AST set mouse point location originalMouseLocation