I need to extract a range of values from variable size data in SIMULINK

I have a matlab function named nodes inside SIMULINK, with one of the outputs named xr. xr is actually a variable sized array with maximum dimensions as 11x1 (set in the ports and data manager).

In another MATLAB function, I require to extract values with index ranging from 2:6. However SIMULINK doesn't allow me to extract this range and gives an error " An error occurred while running the simulation and the simulation was terminated Caused by:

• Code generation assumption about size violated. Unexpected run-time vector changed predicted orientation. "

Can any one guide me how to tackle this issue?