Like that in a grid panel where I have a checkbox that it was possible to select only those that meet a certain condition.

<%@ Import Namespace="System.Collections.Generic" %>


<%@ Register Assembly="Ext.Net" Namespace="Ext.Net" TagPrefix="ext" %>


<script runat="server">
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!X.IsAjaxRequest)
        {
            this.Store1.DataSource = new List<Company> 
            { 
                new Company(0, "3m Co", 71.72, 0.02, 0.03),
                new Company(1, "Alcoa Inc", 29.01, 0.42, 1.47),
                new Company(2, "Altria Group Inc", 83.81, 0.28, 0.34),
                new Company(3, "American Express Company", 52.55, 0.01, 0.02),
                new Company(4, "American International Group, Inc.", 64.13, 0.31, 0.49),
                new Company(5, "AT&T Inc.", 31.61, -0.48, -1.54)
            };


            if (!this.IsPostBack)
            {
                RowSelectionModel sm = this.GridPanel1.GetSelectionModel() as RowSelectionModel;
                
                sm.SelectedRows.Add(new SelectedRow(3));
            }
        }
    }
    
    public class Company
    {
        public Company(int id, string name, double price, double change, double pctChange)
        {
            this.ID = id;
            this.Name = name;
            this.Price = price;
            this.Change = change;
            this.PctChange = pctChange;
        }


        public int ID { get; set; }
        public string Name { get; set; }
        public double Price { get;set; }
        public double Change { get;set; }
        public double PctChange { get;set; }
    }
</script>


<!DOCTYPE html>


<html>
<head runat="server">
    <title></title>
<script>
    var template = '<span style="color:{0};">{1}</span>';


    var change = function (value) {
        return Ext.String.format(template, (value > 0) ? "green" : "red", value);
    };


    var pctChange = function (value) {
        return Ext.String.format(template, (value > 0) ? "green" : "red", value + "%");
    };


    var beforeEdit = function (record) {
        if (record.data.price > 70) {
            return false;
        } else return true;
    };


</script>    
</head>
<body>
    <form runat="server">
        <ext:ResourceManager runat="server" />
        
        <h1>GridPanel with Checkbox Selection Model</h1>
        
        <ext:GridPanel 
            ID="GridPanel1" 
            runat="server" 
            Title="Company List"
            Collapsible="true"
            Width="600">
            <Store>
                <ext:Store ID="Store1" runat="server" PageSize="10">
                    <Model>
                        <ext:Model runat="server" IDProperty="ID">
                            <Fields>
                                <ext:ModelField Name="ID" />
                                <ext:ModelField Name="Name" />
                                <ext:ModelField Name="Price" />
                                <ext:ModelField Name="Change" />
                                <ext:ModelField Name="PctChange" />
                            </Fields>
                        </ext:Model>
                    </Model>
                </ext:Store>
            </Store>
            <ColumnModel runat="server">
		        <Columns>
                    <ext:Column 
                        runat="server" 
                        Text="Company" 
                        Width="160" 
                        DataIndex="Name" 
                        Resizable="false" 
                        MenuDisabled="true" 
                        Flex="1" />


                    <ext:Column runat="server" Text="Price" Width="75" DataIndex="Price">
                        <Renderer Format="UsMoney" />
                        <Editor>
                            <ext:TextField runat="server" />
                        </Editor>
                    </ext:Column>


                    <ext:Column runat="server" Text="Change" Width="75" DataIndex="Change">
                        <Renderer Fn="change" />
                        <Editor>
                            <ext:TextField runat="server" />
                        </Editor>
                    </ext:Column>


                    <ext:Column runat="server" Text="Change" Width="75" DataIndex="PctChange">
                        <Renderer Fn="pctChange" />
                    </ext:Column>
		        </Columns>
            </ColumnModel>
            <SelectionModel>
                <ext:CheckboxSelectionModel runat="server" ID="CheckboxSelectionModel1" Mode="Multi">
                    <Listeners>
                                <BeforeDeselect Fn="beforeEdit" />
                    </Listeners>
                </ext:CheckboxSelectionModel>
            </SelectionModel>            
            <Plugins>
                <ext:CellEditing runat="server">
                </ext:CellEditing>
            </Plugins>
        </ext:GridPanel>
    </form>
</body>
</html>