[Solved] How do I choose the best xlFileFormat for SaveAs

I have a situation where I am creating a new workbook, and assigning a name from an algorithm. When I come to save it, I know exactly the name I want, and that it will be (eventually) an ".xlsm" file.

I've tried saving it with the extension already added in (foobar.xlsm), but I get an error saying that I can't store macros in a plain vanilla spreadsheet (sounds like Excel wants to call the file foobar.xlsm.xlsx).

OK - I have to pick a FileFormat value - but there are so many of them, and the documentation is (surprise,surprise) somewhat less than extensive.

Can anybody give me a clue as to which xlFileFormat value I should supply so that my file ends up as foobar.xlsm?

Thanks, in advance!

Tony