TIWCGJQDatePickerOptions.OnBeforeShowDay Property
The function takes a date as a parameter and must return an array with [0] equal to true/false indicating whether or not this date is selectable, [1] equal to a CSS class name(s) or '' for the default presentation, and [2] an optional popup tooltip for this date. It is called for each day in the datepicker before it is displayed.
published property OnBeforeShowDay: TIWCGJSonFunc index 49 read GetFuncValue write SetFuncValue stored IsFuncStored;