Matlab help on Financial Estimation!!?

Hi, I am trying to use matlab for my financial estimation paper. I am using matlab to find out the probability of default using a DOC model. I am facing issues big time, since it's been almost 3 years since I last used matlab
1. Maximum likelihood estimation:
I am using the equation
ve = va* N(d1)- exp(-rT)*X*N(d2)
where d1 = (log(Va/X)+ (r+(sigma^2/2))*T)/ (sigma*sqrt(T))
and d2 = d1 - (sigma *sqrt(T))
I have the values of ve, X, r and T. I need to find out v, sigma and alpha (a barrier level - a part of a bigger equation) using Maximum Likelihood Estimation (iteratively).
I am trying to use GARCHFIT and MLE functions but they're throwing up errors. I am not able to figure out ow to input arguments to these functions and can't understand what outputs I get
Can somebody please help me on this?
cheers
dB