Rename Roll No

The user enters the old Roll No and the new Roll No and clicks on Ok button, it checks the Roll No exists or not. If it does not exist give the error message ‘Roll No is not processed’. If it is exist then ask the user Are you sure you want to rename the roll no? If the user click on yes then check if the new roll no entered by the user exist if yes then display message "Cannot update new roll no exist" if the new roll no does not exist update the Old Roll Number with New Roll No in the Job Reading table and message is displayed Roll Number is renamed from 99A to 999.