title: If Else Condition in Xml
body: <p>I made a Custom module and I have made a system.xml , in which i am checking whether admin wants to include css or not
  if admin choose one I am including one.css using below cod in my module layout.xml code</p>
  
  <pre><code>&lt;action method="addCss" unlessconfig="mymodule/addcss/one"&gt;&lt;stylesheet&gt;mymodule/test/two.css&lt;/stylesheet&gt;&lt;/action&gt;
  
  
  &lt;action method="addCss" ifconfig="mymodule/addcss/one"&gt;&lt;stylesheet&gt;mymodule/test/one.css&lt;/stylesheet&gt;&lt;/action&gt;
  </code></pre>
  
  <p>now if admin choose no from backend it includes online two.css but when admin choose yes it includes both css one and two..
  i just want to implement if else condition for including different different css .how can i achieve this without using third party extension.</p>