The reason why this is not supported relates to the "Why is there no Derivative block in the component library?" question asked previously.
One workaround would be to add a high-frequency cutoff for the impedance, much as would result in a practical inductor due to parasitic capacitances. The transfer function will be inductive at low frequencies and at higher frequencies the effects of the parasitic capacitances will dominate. Most models should have the order of the denominator greater than that of the numerator.
A more general question is what is the goal of computing the impedance separately, opposed from using the impedance to compute a current value?