There is a trick to incorporate matrix algebra in the model section; in fact one can use any Matlab function.
Using the steps outlined in Steady state file one can manipulate the model_steadystate.m file to incorporate steady state values. Following this advise one can use the parameters of the model to do any kind of Matlab calculations. In my case I do some matrix algebra and define the elements of interest of some matrix as new variables, e.g. A23=A(2,3) where A is a matrix calculated in the model_steadystate.m file. In my mod-file I define A23 to be a parameter. I can then use A23 as a coefficient for a variable in the model section.
Patrick