-- List of key codes:
-- http://macbiblioblog.blogspot.com/2014/12/key-codes-for-function-and-special-keys.html

tell application "System Events"
    -- cmd+arrow down
    key code 125 using {command down}
    -- Just in case
    delay 0.2
    -- cmd+control+, (System Preferences > Keyboard > Shortcuts  > Keyboard > Move focus to next window)
    key code 43 using {control down, command down}
    -- Just in case
    delay 0.2
    -- cmd+arrow down
    key code 125 using {command down}
end tell