Parameter Optimization

Hi everybody, i need help to write a parameter optimization structure for an hydrological model.

I have a model with 3 parameters that have to change in a range that have to be specified; also i have a objective function and a group of functions that constitute the model's "body".

In all the example that i've see the parameters are directly involved in the objective funcion; but in my case the parameters belong to different function of the model's body, and in the objective function only compare the model's output and an input data set.

how can i tell to matlab to minimize my objective function by varying the parameters within the established range ?

hope someone will give me an input! thank you very much.

dario