The dub package in this directory will build an XLL that Excel can load. The functions exported aren't very useful can be found in excel-d's source tree.
Either copy the appropriate (32/64 bit) xlcall32.lib from the Excel SDK
in this directory to build (then either dub build --arch=x86_mscoff or dub build --arch=x86_64)
or make sure it's somewhere that link.exe can find.