One of the arguments corresponds to the source (audio channel) in a k1 hardware synthesizer. The decimal value of the source that goes into the sysex message is 0,2,4, or 6. But for ease of use I want to pass 1,2,3,4 as the value of the source argument to the abstraction, then have math convert that 1-4 value into the even numbers 0 - 6.

Here is a screen shot of the abstraction (k1sx) in the main patch with 3 arguments, 0, 41, 1 (channel number, parameter number, source number).

The abstraction should generate a midi message with the source number converted from 1 to 0 (1 - 1 * 2).

Here is a screen shot of my attempt to do this with an argument within the abstraction, which did not work...

Is there a way that I can take the $3 argument, subtract 1 multiply by 2 and then place this new value as the 2nd to the last value in the message box near the bottom of the patch?