Update vector element Simulink

Hi! I'm using Simulink and Arduino in order to acquire analog signals. I have to elaborate them in real-time, so I have to compute a 125x1 vector that at each sample time has to be refreshed. The problem is that using the Matlab function block I have as output a matrix with a number of rows equal to the time duration divided by the fundamental sample time and 125 columns, i.e. it computes a new vector for each sample. How can I do in order to have as output only a 125x1? Thank you in advance!