Several ways. From the way you wrote the question, I’m assuming you don’t want your answer to depend on dr/dt, so solve both of those equations for dr/dt and then set them equal to each other. This will give you a direct relationship, but it’s up to you what to do with it. You can solve for one in terms of the other, find their proportion, or whatever else.

S = dV/dr

So if you take d/dt on both sides then...?