Solving matrix using LS method in SIMULINK

I have a 90x1 matrix , which is the output of a simulink model at each step time, and i am trying to multiply it to a contant matrix of size 90x4. In the command window i can eaily do it using the "\" operator which gives me the solution of the system using the least squares method. But i am facing problems while trying to implement the same in simulink environment. Can someone suggest any solution to this?