It's funny you should mention this right now--I was just doing a bit of work with Multisim recently, measuring voltage and current as a function of time. I used the Transient Analysis in Multisim to graph it. To do that, you would go to Simulate>>Analyses>>Transient Analysis. You should be able to choose "current" as the output in the "output" tab, then run the simulation.
Come to think of it, you might not need the transient analysis--it depends on the type of function you're expecting.
Regards,
Der Strom