Code (Javascript)

function Zoom(sender, args)
            {
	            var newZoom = sender.get_value();
                var diagramView = document.getElementById("<%= DiagramView3.ClientID %>");
	            diagramView.ZoomFactor = newZoom;
            } 

Code (HTML)

<div style="clear: both; margin-top: 10px; margin-left: 10px; margin-right: 10px;
                    position: absolute;  z-index: 90001;">
                    <ndiag:Overview ID="Overview1" runat="server" DiagramViewID="DiagramView3" JarLocation="./Java/JDiagram.jar"
                        FitAll="true" Visible="true" Style="background-color: white; width: 200px; height: 200px; position: absolute;" />
                        <ndiag:OverviewExtender ID="OvExt1" TargetControlID="Overview1" runat="server" />
                </div>
                <div style="z-index: 90000;">
                    <ndiag:DiagramView ID="DiagramView3" runat="server" Behavior="Pan" ClientSideMode="ImageMap"
                        JsLibraryLocation="./Js/MindFusion.Diagramming.js" JarLocation="./Java/JDiagram.jar"
                        AppletStartedScript="onAppletStarted" ShowScrollbars="true" ShowOverview="false"
                        OverviewFitAll="true" OverviewTitle="Navigator" Diagram-EnableStyledText="true" ZoomFactor="50">
                    </ndiag:DiagramView>
                </div>