codice:
<form name="form1"> 
<input type="radio" name="cucu" value="primo" onClick="if(this.checked){document.form1.bottone.disabled=true;document.form1.CAMPO.value='ciao'}"> 
<input type="radio" name="cucu" value="secondo" onClick="if(this.checked){document.form1.bottone.disabled=false;document.form1.CAMPO.value=''}"> 
<input type=text name="CAMPO">
<input type="button" name="bottone" value="clicca"> 
</form>
GRAZIEEE