I am pleased to note that Dr. Paul Chevrette has posted a user manual and AstronavXIs version 8.0 Excel spreadsheet for downloading at no charge.
AstronavXls navigation software
"This celestial navigation software allows the reduction of sextant sights. The software is based on macro-enabled Microsoft Excel Worksheets. With primary input data from the Nautical Almanac, it gives a graphical representation of the various parameters used in the solution of the spherical navigation triangle, while minimizing the need of correction tables. Up to three sights can be processed and the results are plotted showing azimut lines and circles of position. The intersections of the circles of position are computed, as well as the resulting mean position."