How to create a Dipole on FEKO with varying length

Hi, I'm pretty new to FEKO but as an assignment, our professor wants us to create a dipole and analyze it "over a broad spectrum" On his sample graphs he showed us a plot of the Impedance vs Dipole Length. I was wondering how to do this. I can create a dipole using a fixed length but I can't seem to figure out if it's possible to get the results similar to what he showed to us where the length of the dipole was varying and as a result show the changes in the input impedance as the length changes.

I'd appreciate any kind of help on this matter. Thanks!