update my_fun for lsqcurvefit during runtime

Hi,

I am working on a parameter estimation problem using the lsqcurvefit function. During runtime I want to change the function 'my_test_func' that is used in the fitting. So inside my matlab script I do the following:

for jj = 1:1:10
  % create r
  r = r.';
%%create my fun %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  ni = (jj * 2) + 1;
  name = sprintf('my_test_func');
  ending = sprintf('.m');
  filename = strcat(name,ending);
  fid = fopen(filename,'w');
  insidename = strcat('function [F] =  ',name,'(x,xdata)');
  fprintf (fid,insidename);
  fprintf (fid,' \n');
  final_wort = '  F  =  ';
  for i = 1:ni
    if (i == 1) 
        wort = sprintf(' (x(1) - x(2) * log(xdata(:,%u)/0.8))',i);
    elseif (i > 1) && (i < ni)
        wort = sprintf(' + (x(1) - x(2) * log(xdata(:,%u)/0.8))',i);
    elseif (i == ni)
        wort = sprintf(' + (x(1) - x(2) * log(xdata(:,%u)/0.8));',i);
    end
    final_wort = strcat(final_wort,wort);
  end
  fprintf(fid,'%s\n',final_wort);
  fprintf (fid,' \n');
  fprintf (fid,'return; \n');
  fclose(fid);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%fitting input
% reset
  guess140 = 0.0;
  xdata    = 0.0;
  ydata    = 0.0;

    xdata = [r(:,1:(jj*2)+1)];
    ydata = [observed_data];
  % do the trick
    guess140(jj,1:2) = lsqcurvefit(@my_test_func,[350 8], xdata, ydata); 
  %disp([num2str(guess140),' XXXXX ',num2str(jj)])

end % jj

My problem is that lsqcurvefit is not using the current 'my_test_func' but the very first one. How is it done correctly? Is there a way to update 'my_test_func' during runtime (within a loop)? Thank you in advance.

Eide