Hello Khaled,

You can hide some of the check boxes by handling the InitializeRow event of the WebDataGrid and setting a css class to some of the cells. For example if you want to hide the checkboxes of every second row you can try the following:

    protected void WebDataGrid1_InitializeRow(object sender, Infragistics.Web.UI.GridControls.RowEventArgs e)
    {
        if (e.Row.Index % 2 == 0)
        {
            e.Row.Tag = true;
            e.Row.Items[3].CssClass = "disabled";
        }
    }

in css:

    <style type="text/css">
    .disabled
    {
        visibility:collapse;
    }
    </style>

For additional reference you can check the attached sample.

If you need any further assistance on this do not hesitate to ask.