Differential Equation problem. ~Please help

Hi. I have the following code:

function dydx = vdp1(x,y)
dydx = [y(2);-y(1)];

And in another script I have the following code:

sol = ode45(@vdp1,[0 pi],[0;1]);
xint = pi;
Sxint = deval(sol,xint)

However I want to introduce a variable w so that the differential equation becomes:

dydx = [y(2);-(w^2)*y(1)];

and my result is in terms of w. I have been trying this for hours but to no avail. Any help would be great. Thanks

[Azzi Abdelmalek]

is w variable or constant, if variable, how w is varying?