codice:
<form name="modulo">

<INPUT type=radio name="radio" OnClick="javascript:document.modulo.testo.value=this.value;" value="primo">
<INPUT type=radio name="radio" OnClick="javascript:document.modulo.testo.value=this.value;" value="secondo">



<input type="text" value="primo" name="testo">
</form>
Ciao Ciao