It would depend on you as the designer to where the code goes.
If you wanted to save the date in this format it would have to be formatted elsewhere e.g. from an afterupdate on the control.
You might want to have a visible control on the form where the user inputs the normal date and then the control applies the format and puts it in another control bound to the table.
It could go on the form's ONOpen property where it could fill an unbound visible property if it was today's date you were using. e.g.
Me!MyDate= UCase(Format([Date()],"mmmm"", ""dd"))
The options are almost endless....
Try experimenting with some of the above.
If you want to describe the actual way you intend to use the format, somebody will, no doubt, give you a more specific response.
HTH
Dave E