Apparently, you are solving an ODE by forward Euler steps. Don't do that. It is both inaccurate and wasteful of computer time. I refer to these steps in your code:
dydt = odes (t, y0);
y = y0 + dydt' * Delt;
Instead, you should call ode45 to solve your ODE.
You also have many more global variables than you need, but that is a discussion for another time.
Now for the question you asked. I get an error when running your supplied code:
Error using lsqfcnchk (line 108)
FUN must be a function, a valid character vector expression, or an inline function object.
Error in lsqnsetup (line 46)
funfcn = lsqfcnchk(FUN,caller,lengthVarargin,funValCheck,flags.grad);
Error in lsqcurvefit (line 201)
Error in mytry (line 483)
Specifically, your Results argument is not a function handle. lsqcurvefit needs to be able to change the parameters and rerun your calculations to fit the function to the data. So I am not completely sure what you are trying to do, but you haven't supplied us with working code to check.
MATLAB mathematical toolbox documentation