Dropdown list with multiple items

How can I replace the comma before the last item in a multiple-item drop-down menu with 'and'?
At present, I have x, y, z, and 'and' as the options. If I include 'and' as one of my choices, I get 'x,y, and, z.'
If I don't choose 'and', I get 'x, y, z'.
Neither is grammatically correct. I'd like 'x, y and z'. Or include an 'Oxford comma' thus, 'x, y, and z.'
Any suggestions?

Hi Amanda,
You can use BLAZE_AND or BLAZE_OR with Special Delimiters

Here is a sample of how to use a Dropdown list

You have selected {formmenu: a; b; c; default=x; default=y; z; name=options; multiple=yes; formatter=(value) -> join(value, "BLAZE_AND")}

or you can have the format outside the menu so you can have more control on how you use the list. I wrapped {formmenu} inside {note} so it will be hidden.

{note}{formmenu: a; b; c; default=x; default=y; z; name=options; multiple=yes}{endnote}You have selected {=join(options, "BLAZE_AND")}