format optional parameter

[compound]

I've seen a long time ago that optional parameters in the user defined
function could be italicizes in the Function arguments window in excel.

This is what I'm trying to achieve.
If I have a function MyFunction(byval TradeDate as date, optional byval
Price as double = 0) then if I go in to spreadsheet and insert function
MyFunction into a cell and then open function arguments window then
"TradeDate" argument will look bold and "Price" argument will look Bold and
Italic.

Thank you!
Compound.