Look at the source.
They did not hide their javascript code.
So I think that, with your programmer experience, (maybe print it
first) you'll be able find the formula your looking for and then
figure out how to write it for Excel.

Since javascript is much more familiar to me then VBA, if you don't
find, tell me exactly which option(s) you would select, and I'll find
the formula for you. I'd be so happy to be able to help for once!