Visual Basic Using Visual Studios Data Grid View Selected Index Changed Updating?

when the user clicks on the add button another form launches, which enables the user to add student info such as name, address, course, start date and end date, this information is then written to class when the ok button on that form is clicked, and then displays the data on the initial form in data grid. the user can add multiple entries and they are all displayed on the intial form and a the data grid is populatedwhen any of the rows in the displayed grid is selected, and the update button is clicked then the same form launches as the previous one and but this time its in the update mode and pre populates the form with the inital values.