tell application "System Preferences"
activate
set the current pane to pane id "com.apple.preference.keyboard"
reveal anchor "keyboardTab" of pane id "com.apple.preference.keyboard"
end tell

tell application "System Events" to tell process "System Preferences"
    delay 0.3
    set thePopUp to pop up button 2 of tab group 1 of window "Keyboard"
    set current to value of thePopUp
    click thePopUp
    if current is equal to "F1, F2, etc. Keys" then
        click menu item 1 of menu 1 of thePopUp
    else
        click menu item 3 of menu 1 of thePopUp
    end if
end tell

quit application "System Preferences"