A family of Microsoft relational database management systems designed for ease of use.
George
Unfortunately, the date picker only works on form controls that are bound to a date field. There are lots of custom forms made to mimic the date picker. A good site to check is http://www.accessmvp.com/JConrad/accessjunkie/calendars.html
Using one of those calendar forms, you would create a form with a text box on it. Then use a calendar form to get a selected date into that text box. Then change your query parameter to use that text box as the prompt.
The prompt would be:
[Forms]![YourFormName]![YourTextBoxName]