Hi Bala,
this is coding---
public static void main(String args[]) throws Exception 
{     SetTest st = new SetTest();     st.addDaysToDate
("28/04/2009", 4);} private void addDaysToDate(String date, 
int daysToAdd) throws Exception {     Date todayDate = new 
Date();     DateFormat sdf = new SimpleDateFormat
("dd/MM/yyyy");     String strDate = sdf.format
(todayDate);     Date parsedDate = sdf.parse(date);     
System.out.println(strDate);     System.out.println
(parsedDate);      Calendar now = Calendar.getInstance
();     now.setTime(parsedDate);      now.add
(Calendar.DAY_OF_MONTH, daysToAdd);     System.out.println
(now.getTime());}

there is one adddate funtion in qtp u can use that function 
for more detail see date and time function in qtp help
please let me know if u still have any doubt
thanks 
rahul pandey
writetorkpandey@gmail.com