If u r using jsp page means v can easily changing the frame size at runtime.
<%!
int size=100;
%>
<frameset border="0" rows="<%size%>,230">
<frame src="JSP_1.jsp" name="FRAME_NAME_1">
<frame src="JSP_2.jsp" name="FRAME_NAME_2">
</frameset>
</frameset>
If u change the value of"size" that frame size will b change.