this can be a solution

vb Code:
  1. private str as string = "abc" 'at least two characters in the string
  2. private counter as integer = 0
  3.  
  4. private sub form_load(Sender as object, e as eventArgs) handles Form1.Load
  5.   Sound(str.Chars(counter))
  6.   counter += 1
  7. end sub
  8.  
  9. private textBox1.keyPress(Sender as object, e as ByVal e As System.Windows.Forms.KeyPressEventArgs) handles TextBox1.KeyPress
  10.       sound(str.Cahrs(counter))
  11.       counter += 1
  12.  
  13.   if counter = str.length then
  14.     messageBox.Show("Something")
  15.   ens if
  16. end sub