Prova cosi:
codice:
<script type="text/javascript">
function AbilitaOnly(ele){
if(document.getElementById(ele.id).geAttribute("readonly") == 'readonly')
{document.getElementById(ele.id).removeAttribute("readonly");
}else{
document.getElementById(ele.id).setAttribute("readonly","readonly");
}
}
</script>
<input name="g_p" type="text" readonly="readonly" ondblclick="AbilitaOnly(this)" id="id_g_p" value="<%If TPTV = "si" Then Response.Write("") Else Response.Write(arrTPT(1,0)) End if %>" size="4" maxlength="2" />