Código HTML:
<html> <head> <title>Untitled Document</title> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <SCRIPT LANGUAGE="JavaScript"> function mifuncion(form){ temp = form.combo.value form.caja.value = form.caja.value + "<br>" + temp; } </SCRIPT> </head> <body bgcolor="#FFFFFF" text="#000000"> <form name="form" method="post" action=""> <p> <select name="combo" > <option value="Valor1">Valor1</option> <option value="Valor2">Valor2</option> <option value="Valor3">Valor3</option> <option value="Valor4">Valor4</option> <option value="Valor5">Valor5</option> <option value="Valor6">Valor6</option> </select> <label> <input type="button" name="Submit" value=">>" onClick="mifuncion(form)"> </label> <textarea name="caja"></textarea> </p> <p> </p> </form> </body> </html>