You have some function that evaluates the objective, right? Maybe an interpolation as in the Mount Washington example. Toolbox functions don't care what the objective function is, they just need to be able to get function evaluations.
If your objective function is not smooth, as often happens when the evaluation is a simulation or numerical solution of an equation, then you might need to set the finite differences to be larger than default. use the FinDiffRelStep or DiffMinChange options. Or use patternsearch if you have Global Optimization toolbox.
MATLAB mathematical toolbox documentation