Can I pass local time step to another function?

I am using a boundary value solvers to calculate the solution of BVP:

d2u/dx2=-S(x)

The source term is calculated by a complicated function and to make the units consistent and physically meaningful, there is need of a division to local time step (or in my case \delta x) within the source term calculation.

Can anybody please lead me how to pass the time step to derivative function (such as twoode in the help pages)?

Here is the code I am using, please not that the actual code is much longer but I believe this one represent my problem:

% solve the boundary value problem

options = []; % bvpset %place holder

solinit = bvpinit(linspace(0,L_y,n_y),[1 1]);

v_z = bvp5c(@ode_vz,@ode_vz_bc,solinit,options);

% ------------------------------------------------------------

function dydx = ode_vz(x,y) S=calculate_source(x); % see the fucntion below to look at the calcuations for the source term dydx = [ y(2) -S]; end

% ------------------------------------------------------------

function res = ode_vz_bc(ya,yb) res = [ ya(1) yb(1) ]; end

% ------------------------------------------------------------

function force=calculate_source(x) % Calculates source term % more calculations are here

force=f_d* h_c/(d_b * (1+s_p) ) / mu_l / ( (I want to add the local time step here) *d_b*L_z*1e-9); % [N / mu V} or [1 / m s]

end