Outlook itself does not include any date picker control (which, by the way, is one reason why the first page of the appointment, journal, and task forms is not editable). See http://www.outlookcode.com/d/datepick.htm for controls you can add.

Also, you'd have to write VBScript code behind the form to create appointments for each extra date field. I'd recommend using the Item_Write event handler.

FYI, there is a newsgroup specifically for Outlook forms issues "down the hall" at microsoft.public.outlook.program_forms or, via web interface, at http://www.microsoft.com/office/community/en-us/default.mspx?dg=microsoft.public
.outlook.program_forms