Security :: Membership Change Email Of A Selected User?

change details of a user ( asp.net membership change email of a selected user ).

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Protected SubButton4_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button4.ClickTry Email = EmailTextBox.Text Membership.UpdateUser() updateuserlabel.Text = "User e-mail updated." Catch u As System.Configuration.Provider.ProviderException
updateuserlabel.Text = MessageEnd
End Sub

This works but what is does is to load the email of the user that is login to the textbox and then if i press the button it changes to the text assign to the textbox.What i want is to choose from all the system users and then change the email of each.