Estimation of non linear model with two summation in the Likelihood function

Hello guys, i’m Adzhar from University of Malaya, Malaysia. I really need your help or guidance how to find estimate parameter using MLE method. Before this i’m using Minimize Sum (MS function in s-pluss) to get the estimation but this time my model has two summation which is can’t be solve using Minimize Sum. Do you have any packages available regarding to this matter? I’m really thankful if you can help me.. Please feel free contact me if you want to look at the model then i,ll email to you guys.

Thanks

Adzhar
University of Malaya
Malaysia