I can't include tags at runtime!!!

Hello! 

I'm the first time here  

I tried to include a tag, consists of button tags, which i will include to an  
 
existing panel tag. 

pseudocode: 

file_1.xml 
######### 
<panel id="test" include="file_2.xml#but"> 
       <!--buttons after rendering the xml file --> 
</panel> 
######### 



file_2.xml 
####### 
<button id="but" icon...  action.../> 
<button id="but" icon...  action../> 
<button id="but" icon...  action.../> 

I can't see the included Buttons. What is the problem? It's impossible to   
include Button tags? 

Thanks in advance. 
Regards 
Erik