themes using tiles instruts

[vasu pyla]

Hi all.i am working in struts framework.i don't no how to add the extra themes in my tiles-defs.xml.My tiles sheet given below.so please help me

<definition name="layout" path="/layout.jsp">
<put name="title" value="Helix - Medical ERP Solution" />
<put name="header" value="/header.jsp" />
<put name="latestcalender" value="/latestcalender.jsp" />
<put name="topMenu" value="/topMenu.jsp" />
<put name="leftMenu" value="/leftMenu.jsp" />
<put name="content" value="/index.jsp" />

<put name="jscript" value="/mainJs.jsp" />
<put name="styles" value="/styles.css" />
<put name="tabs" value="/style1.css" />

<put name="tooltip1" value="/js/dw_event.js" />
<put name="tooltip2" value="/js/dw_tooltip.js" />
<put name="tooltip3" value="/js/dw_viewport.js" />
<put name="tooltip4" value="/js/overlib_mini.js" />
<put name="tooltipbody" value="/tooltip.jsp" />



</definition>

In my project i am using (styles.css & style1.css) and how can i implement themes using the above xml file.