EZWires and EZPlots are two Excel spreadsheet programs that are designed to extend the capabilities of the EZNEC Version 3 antenna modeling package.
EZWires helps on the "input side" by letting you do "Modeling-by-Equation" with EZNEC. You can define the wires of your antenna model using a pair of enhanced spreadsheets and then pass the wire set over to EZNEC to complete the simulation. The program comes with several samples, including quads, a delta loop, an octagon helix, and templates that may be used to quickly build 40 of the ARRL Optimized Yagis.
EZPlots helps on the "output side" of EZNEC by offering a convenient way to plot many of the data items that can be produced with an EZNEC frequency sweep. EZNEC itself can plot SWR versus frequency and can show far field trace overlays for different frequencies. With EZPlots you can see additional items such as source R and X versus frequency or Forward Gain and Front/Back Ratio versus frequency. You can "take a snapshot" of any plotted line to allow easy A/B comparisons between modified versions of the same model or even between two completely different antennas.
More information and a zip file for download may be found at http://www.qsl.net/ac6la/ezwpintro.html