[andy.s]

local function choices()
    return {math.random(100), math.random(100)}
end
 
{
    type = "dropdown",
    -- name, getFunc, etc...
    setFunc = function(value)
        MyAddonDropdown:UpdateChoices(choices(), choices())
    end,
    choices = choices(),
    choicesValues = choices(),
    reference = "MyAddonDropdown",
},

This code randomizes MyAddonDropdown items every time you select something.