Midish "If" functions

Hi!

I really appreciate if you could advise me if Midish can do what I need.

I have a stage piano and a synth working together in live performances. I
would like to set up both instruments with only one touch. Stage piano only
can be programmed to send to the synth MSB, LSB and PC numbers, but the
synth needs to receive a certain SysEx message to switch between diferent
modes. So, from the stage piano, I can change synth´s sounds but not the
mode.

I was thinking on using a RaspberryPi with Pisound card to route ALL
signals from the piano to the synth and viceversa, but be able of sending a
certain SysEx message when a specific MSB message will appear at the input.

I can send a package of MSB, LSB and PC messages from the Stage piano, but
Synth only responds to PC changing, so maybe I could use MSB or LSB to make
Midish send the SysEx that synth needs to change between modes (and of
course PC).

In my mind, it implies the usage of "if" functions (or similar), but I
cannot find nothing familiar within the manual. Could you give me an advise?

Is PiSound card compatible with this software running on Raspbian?

Many many thanks in advance!

Best regards.

Daniel