Richard, I don’t have an excel sheet, but I use an app called iSailGPS.  It lets u download charts and set waypoints by lat/long as well as bearing & distance from position/WP. 

Once the new WP is created, you can see its coordinates in the WP’s data. 

.... you can export your WP’s as a KLM file, then import that into Excel. 

Check e trap.

I have the marklaying spreadheets  which give bearing and distance from the reference point, but they don't calculate the lat and long of the course marks.

Not a simple formula.  Lines of latitude are all the same distance apart on the globe,  but lines of longitude get closer together as you move away from the equator.  There is a relatively simple formula to determine distance between longitude at a given latitude here.  Scroll down to the section "Lengths of a degree" and use the WGS84 datum formula which is what your GPS is probably set to.  If you just need this for a local racing area it might be easier to just calculate an average distance between lines of longitude using a map or a charting application.  Then build the spreadsheet using typical cartesian maths.  You may be able to find a spreadsheet already built for your purpose online.    

For what purpose are you developing this?

If it's to generate lat/lon of marks - any MBO knows it's far easier and more accurate to find a position relative to a reference point (driving away from it) than to find a specific reference point (driving towards it).  Due to the inaccuracies of GPS, you'll end up "circling the drain" trying to drive to a reference point.  You'll get within 10 meters or so, but that's about all the accuracy you can expect.

Here's a simple one that (at least) works well in Scandinavian waters: ☒

Niklas
We only got  the name of the spreadsheet.  I cannot download that.  Can you provide a link to the spreadsheet or macro?
Thanks,
Lloyd