Hi Cgvak,

You may use set_size member of Infragistics.Web.UI.SplitterPane class. Example:

 <script type="text/javascript">
 function resizeSplitter()
 {
  var splitter = $find('<%=WebSplitter1.ClientID%>');
  var pane = splitter.get_panes()[0];
  pane.set_size(100);
 }
 </script>
 <input type="button" value="resize splitter" onclick="resizeSplitter()" />