MATLAB: How to create/access and update global variables in Simulink using Data Store Memory block

MATLAB and Simulink Student Suitesimulink

In the Simulink Model (.slx attached), I would like to create a global variable 'Pulse' which I have attemped doing in the MATLAB function block. I further would like to update this variable such that at each iteration of the simulation, the updated variable is used by the MATLAB function block. I have added the Data Store Memory block to the model, however the model returns the following erroe for the above mentioned steps take:
Simulink cannot determine sizes and/or types of the outputs for block 'globalSimulinkData/MATLAB Function' due to errors in the block body, or limitations of the underlying analysis. The errors might be inaccurate. Fix the indicated errors, or explicitly specify sizes and/or types for all block outputs.
The variable 'Pulse' is initialised in the MATLAB script as 'PulseInit' (.m file attached).