有熟悉ext 的人近来帮下忙


<ext:GridPanel 
            ID="GridPanel1" 
            runat="server" 
            Title="消息管理"
            Frame="true"
            StoreID="Store1" 
            AutoHeight="true" 
            AutoWidth="true">
                       
            <ColumnModel ID="ColumnModel1" runat="server">
                <Columns>                    
                    <ext:Column DataIndex="Title" Header="标题">
                        <PrepareCommand Args="grid,command,record,row,col,value" FormatHandler="true" Handler="window.location.href('?command=state3')"></PrepareCommand>
                    </ext:Column>
                    <ext:Column DataIndex="Sent" Header="发送人">
                        <PrepareCommand Handler="" Args="grid,command,record,row,col,value" FormatHandler="False"></PrepareCommand>
                    </ext:Column>
                    
                    <ext:CommandColumn Width="150" >
                        <Commands>
                            <ext:GridCommand  Icon="NoteEdit" CommandName="update" Text="修改" Hidden="true"  />
                            <ext:GridCommand Icon="Delete" CommandName="delete" Text="删除" /> 
                            <ext:GridCommand Icon="ApplicationGo" CommandName="select" Text="详情" />                          
                        </Commands>                    <PrepareToolbar Handler="" Args="grid,toolbar,rowIndex,record" FormatHandler="False"></PrepareToolbar>                    <PrepareGroupToolbar Handler="" Args="grid,toolbar,groupId,records" FormatHandler="False"></PrepareGroupToolbar>
                    </ext:CommandColumn>
                </Columns> 
            </ColumnModel>
            
            <SelectionModel>
                <ext:CheckboxSelectionModel />
            </SelectionModel>
            
            <LoadMask ShowMask="true" />
            <BottomBar>
                <ext:PagingToolBar ID="PagingToolBar1" runat="server" PageSize="10" StoreID="Store1" RefreshText="刷新"/>
            </BottomBar>
            <Listeners>
            <%--用户ID = record.data.UId  cmd 来自command--%>
                <Command Handler="window.location.href('?id='+ record.data.MessageId + '&command=' + command)" />
            </Listeners>        </ext:GridPanel>我想在代码里控制 <ext:GridCommand  Icon="NoteEdit" CommandName="update" Text="修改" Hidden="true"  />这个控件的Hidden属性,用什么方法合适?