How do I reference an undefined variable in an ode45?

Hi, so I've looked around, and I haven't been able to find anything that gives an answer to my question.

Anyway, I'm trying to reference a rate that is a function of time in a ode45 evaluation of a system of differential equations. My actual model is way to long to bother you guys with, so I wrote a very simple version of what I want to do.

    Pmax=2;%Sets max of P curve
    meantime=12;
    omega=meantime/3;
    syms t
    P=Pmax*10*exp(-((t)-meantime).^2/(2*omega^2))/(omega*sqrt(2*pi));
    kwash=.5*P;
    %What I want to do:
    %xprime=@(t,x)[kwash*x(2);-kwash*x(2)];
    %What I have to do:
    xprime=@(t,x)[.5*(Pmax*10*exp(-((t)-meantime).^2/(2*omega^2))/(omega*sqrt(2*pi)))*x(2);-.5*(Pmax*10*exp(-((t)-meantime).^2/(2*omega^2))/(omega*sqrt(2*pi)))*x(2)];

    x0=[0 100];
    tspan=[0:.01:24];
    [t,x]=ode45(xprime,tspan,x0);

As you can see, I want reference a time-dependent rate in the transfer equation instead of writing it out within the xprime input. Obviously, I can just write it out here, but my real transfer system is very large and references a number of variables that would be time dependent. As you can see, I treat t like a symbol. My idea was to use matlabFunction to plug it into the xprime, but because xprime is a function itself, that doesn't fly. Also, I need to use an ode of some sort, because my real system cannot be solved using a Dsolve.

Anyway, I hope this makes sense.

Thanks,

John