I'm not sure if it will help you because to my knowledge the Rio Remote has no "source" button which toggles between tuner and player. Here are the codes we know about from Frank's documentation. This doesn't mean that's all of them.

It would, with some kernel hacking, be possible to have the incoming code translated to two different codes depending on the state of a "flag" variable... something like

flag = 0

if ( input_code = SOURCE )
if ( flag = 0 )
then
output_code = RIO_TUNER_SRC_BUTTON
flag = 1
else
output_code = RIO_PLAYER_SRC_BUTTON
flag = 0
endif
endif



Obviously not a "stock capability" of the IR trans, though.