Hi,
There is MATLAB class “gbm” to create Geometric Brownian Motion object. There are functions like simulate, simByEuler, simBySolution that can be used with gbm object for simulation. Here is the link for the documentation for further details:
Also, you may set the parameters to get your desired behaviour as follows:
dt=1;
nPeriods = 5;
T = nPeriods * dt;