Gradient of a predefined function

Can i obtain the gradient of the following function using matlab :

function MSE=mseFunction(alpha,beta,Data)
.
.
.
MSE = mean((Data(26:264)-PREV2(26:264)).^2);

Thanks

[Walter Roberson]

Question was effectively replaced by the more complete http://www.mathworks.com/matlabcentral/answers/310813-calculate-the-numerical-hessian