Hi,
this schould be possible. I use changing articulations with expressiontext in Sibelius a lot.
For example:
Matrix 1 is Orchestral Strings, Matrix 2 is Camber Strings.
Below the note where I want the switch to take place I insert an expressiontext:
divisi ~CC25,1
Controller 25 being the controlIer I set up to switch between matrixes.
unisono ~CC25,0
switching back to Matrix 1 and therefore to the Orchestra strings.
Of course you can do this with any controller-setup, and even within a matrix.
I hope I undestood your question right and the answer helped.
Best Stefan