HFSS - Can I make a parametric sweep variable dependant on frequency?

Basic question

I want to draw a model in HFSS, with one of the parameters being a length 'L'. A want to sweep the frequency over a range (say 3-6 GHz), but have the length L always a half wave long. So a table of L vs frequency would be:

1. 3 GHz - 50 mm
2. 4 GHz - 37.5 mm
3. 5 GHz - 30 mm
4. 6 GHz - L=25 mm

Is there any way to do this using the Optimetrics in semi-sensible way? If I test at 20 frequencies, I could create 20 models, with each one having a different value of L, and solving them one after the other. But that would be a tedious and error prone way.

Background

I want to estimate the fringing capacitance of an open 'N' connector at the reference plane. I've attached a picture of the N connector, showing the reference plane. Since the reference plane of a male N is at the very front of the RF bits of the plug, it's impossible to put a wave port there. So I thought I'd put a bit of coax on the plug, and make that coax of such a length 'L' that it is always exactly λ2. Then the impedance measured at one end of the coax is the same as would be at the reference plane, since a half--wave will just repeat the impedance. I've no idea if that actually holds or not.

Next question
Does anyone know of a better way I can use HFSS to find the fringing capacitance of a connector like the N?

Yes, u just need to define the length and then sweep over all combinations of freq and L, while setting L=lda/2. lda is wavelength which is a variable in freq domain.