Pavan,
The Agentry calendar control is tied to an object collection. The objects show up on the correct calendar day based on a Date/Time property in the object that you specify on the Calendar View Data tab on that control. I don't believe there is any way to return the Date from the calendar if there are no objects tied to the selected date. If there are objects on the date and you want to access the date: Target: Calendar Screenset -> Calendar Screen -> Calendar Field -> First Selected Object -> DateTime Property. You can target this in a screen update rule, initial value for a transaction property, etc...
Jason Latko - Senior Product Developer at SAP