I haven't tested this yet, so I might be wrong.

The only way I can think of doing it, is to park at the Gate, shut down the plane, or at least turn the IRS OFF. Turn the IRS back ON, then use the second plan (providing it doesn't go missing when turning the IRS OFF). I know that if you were to do a complete shut down of the 767 you would lose your flight plans (RTE1 and RTE2), because I accidentally did it a few times. :-[

Mark