solving dx/dt = x*f(x)

I'm pretty new to matlab and trying to figure out how to solve a diffeq that boils down to dx/dt = x*f(x). I should note that I'm competent enough that I can solve the simpler dx/dt = f(x). F(x) is complicated and it's solution (as currently written) calls upon several layers of functions. In other words, f(x) calls upon function a, which calls upon both the quad function and function b, which calls upon function c. The problem is that function c must be solved simultaneously with the original ODE because they both depend on x. How do I solve function c and my original ODE simultaneously? I hope this makes sense. Thanks in advance...Matt