How can I by pass a parameter?

I have two parameters in my reports. The first parameter is a select menu the second is a date range. How can I by pass the date range if a user only wanted to use the first parameter?

Thanks for the reply.

The first parameter is a simple menu selection. If the first item in the menu is selected then it returns the report without passing any parameter. If the second menu item is select then it uses the values that was entered manually into the date range parameter and generates the report based on that information.