get data from textbox on form pop up using thickbox

 cara pertama dengan alt tag:  
 jsnya :  
 <script type="text/javascript">  
       function GetLinks(i,vsid) {  
         document.getElementById("btn"+i).alt = "packageBookingRes.aspx?vsid="+vsid+"&BPax=" + document.getElementById('txtBookingPax'+ i).value + "&keepThis=true&TB_iframe=true&height=450&width=605";  
       }  
   </script>  
 htmlnya :  
 <input type=\"button\" id=\"btn" + i.ToString() + "\" onclick='GetLinks(" + i.ToString() + ",\""+vsid+"\")' class=\"thickbox sendbook\" value=\"Booking\" />  
 ---------------------------------------------  
 cara kedua dengan tb_show :  
 jsnya :  
 <script type="text/javascript">  
   function GetPax(i, vsid) {  
     if((document.getElementById('txtBookingPax'+i).value != "0")&&(document.getElementById('txtBookingPax'+i).value != "")){  
       var pax = document.getElementById('txtBookingPax'+i).value;  
       tb_show('Booking', 'packageBookingRes.aspx?height=350&width=605&inlineId=CHANGE-ME-INPUT-ID-OF-BUTTON&modal=false&BPax='+pax+'&vsid='+vsid, null);  
     }else{  
       alert('Please input number of Pax!');  
     }  
   }  
 </script>  
 htmlnya :  
 <input type='button' value='Booking' onclick='GetPax(" + i.ToString() + ",\""+vsid+"\")' class='sendbook'>