[NEST Users] Custom input for neurons

Dear all, I'm new at NEST, and I've been trying to recreate a neural system from my work. This involves an IAF neuron which receives two different stimuli (they would be represented by inputs to the neuron - increases in post-synaptic potential). Since these are stimuli I control in my experiments, I need to be able to control their dynamics as the simulation progresses (for example, one of the stimuli has an exponentially larger effect as time progresses). Therefore, it's important for me to be able to control the dynamic of these inputs. However, I have not been able to find a way to do this. One idea I've had is to set the amplitude of a noise-generator to change according to a function of my choosing (going back to the previous example, it would be an exponential function). But this would require for this parameter to be changed mid-simulation, or to be assigned to a function and interpreted by NEST. Is any of this possible? Or alternatively, do you know of another way of accomplishing this? Thank you! Nicolas