keypress in C#

[hoobas20]

here's my code:

 private void keypress_charOnly(object sender, KeyPressEventArgs e)
        {
            

            int ascii = Convert.ToInt16(e.KeyChar);
            if ((ascii >= 97 && ascii <= 122) || (ascii == 8) || (ascii >= 65 && ascii <= 90))

                {
                    e.Handled = false;
                }
            else
                {
                    e.Handled = true;

                }
               
         }

my question is, how can i prevent user to input integer values.
copy and paste (using mouse) can bypass the keypress event..
thanks.