Determine parameters using MATLAB

I want to determine some parameters that compound my equation. I know a little bit about optimization toolbox.

This my code:

G=26.9;
sigma=25;
u=0.4;
sigmam=9.333;

      sigma_star=sigma*((2/3)*(1+u+3*(1-2*u)*((sigmam/sigma)^2)))^0.5;
      D=1-(1-(r+1)*((sigma_star/B)^r)*t)^(1/(r+1));

      et=(sigma/c1)*(1-exp(-G*t/c2));
      es = a1*(sigma^n)*t;
      ed = a2*((sigma/B*(1-D))^n)*t;

      e=et+es+ed;

I have the values of t (time) and e(total deformation) from an experimental test and need to determine a1,a2,c1,c2, B, n and r parameters.

Can anyone give some help in terms of procedure to be adopted to estimate those parameters using MATLAB ?

Thanks.

[Varun Garg]

I don't have much idea about optimization toolbox but i think this thread might help.