pass output between two ode15s

hello

I want to pass output from ode15s in any time step. for example I have two function

xdot2+xdot=Vo (function1)

Vodot+Vo=x+sin(t) (function2)

I doesn't want to use 1 ode15s and combine my function.I want to use 2 ode15s

in time step t(i) must be calculate x(i) is 1th ode15s

[x,t]=ode15s(function1,[tspan],x0)

then call back this x(i) to 2th ode15s to calculate Vo(i)

[Vo,t]=ode15s(function2,[tspan],x0)

and iterate this procedure to t(end)

Would you please help me how can I do this?

[Torsten]

And why don't you want to solve for x and Vo simultaneously ?

Best wishes

Torsten.

[naser]

actually i have second orde ode and i want to solve 1st ode using neamark algorithm. i have large sparse matrix ode for example 20000*20000.when i want to use ode15s for solution i must convert second orde ode to first order ode and this would be 40000*40000.so ode15s has out of memory