Introduce a while loop ina ode45 resolution

Hello, I am a new user of Matlab and I am facing difficulties while trying to introduce a while loop in a differential resolution. My code is this one :

 function [dy] = vdp1(t,y,Vent)
Cx0 = 2;
Cx1 = 0.8;
Syz = 2;
Sxz = 2;
Sxy = 2;
S1 = 75;
tf1 = 4;
m = 15;
M = 80;
Latitude = 69.5;
dy = zeros (6,1);
D = (sqrt(y(1)^2 + y(2)^2 + y(3)^2))/(2*(m+M));
dy(1) = -1.225*Cx0*Syz*D*y(1) + 2*10^(-5)*sind(Latitude)*y(2) - 2*10^(-5)*cosd(Latitude)*y(3);
dy(4)= y(1);
dy(2) = -1.225*Cx0*Sxz*D*y(2) - 2*10^(-5)*sind(Latitude)*y(1);
dy(5) = y(2);
dy(3) = -1.225*(Cx0*Sxy + t*Cx1*S1/tf1)*D*y(3) + 2*10^(-5)*cosd(Latitude)*y(1) - 9.81;
dy(6) = y(3);
end

function [x] = Position(tf1)
x0=[77 0 -2.4 0 0 4000];
t0=0;
tfin=tf1;
[t,x] = ode45(@vdp1,[t0 tfin],x0,[]);

end

I would like to know if it is possible to insert a while loop saying something like : while y(6) is higher than a certain altitude then solve, else the resolution is over.

Thank you for all the help you could give me.

Answer 1

[Jan]

This seems to be a job for the event function. See odeset for setting such a funtion. See also https://www.mathworks.com/help/matlab/math/ode-event-location.html.

Note: 2*10^(-5) is an expensive power operation, while 2e-5 is a cheap constant, which saves run time.

[Lancelot Ribot]

Thank you for your answer !! I am going to read this page carefully

P.S : thanks for the tip