Ok, ti ringrazio.

Allora se ho:
Codice PHP:
function SetActiveID_2(me,ID){
    var 
id=(me.name.substr(12,14));
    
document.getElementById("nasc_new").value me.name;

e poi:

Codice PHP:
echo   '<td id= "ID" onclick="SetActiveID_2(this,ID);" onFocus="SetActiveID_2(this,ID); "  name ="'.$USER['USERNAME'].'">' .$USER['USERNAME']. ' </td>'
E QUINDI:

Codice PHP:
<form action="pippo.html" method="GET">
<
input  type="text" id="nasc_new" name="idchanged" value="">
<
input type="submit">
</
form
perché non mi funziona?