Change width of div not working for child

Question

I have Kendo Splitter with the following structure (simplified):

<div id="MainSplitter style="height:10px;overflow:visible">
   Contains two horizontal panes and the splitter element
</div>

How do i modify the "Mainsplitter" width so the panes also reflect the change, and the Mainsplitter resizes if the browser window size is changed also.

Note: If i change the width of the Main splitter the overflow of the panes in the div gets active after a the first server ajax call. (does this makes sense?)