mailMerge1.LoadTemplateFromMemory(data,
            TXTextControl.DocumentServer.FileFormat.InternalUnicodeFormat);

// load the XML file
DataSet ds = new DataSet();
ds.ReadXml(tbDatabaseFile.Tag.ToString(), XmlReadMode.Auto);

// add the relations for the nested blocks
DataRelation relation_sick = new DataRelation("sick",
    ds.Tables["employee"].Columns["dyn_employee_number"],
    ds.Tables["sick"].Columns["dyn_employee_number"]);

DataRelation relation_vacation = new DataRelation("vacation",
    ds.Tables["employee"].Columns["dyn_employee_number"],
    ds.Tables["vacation"].Columns["dyn_employee_number"]);

ds.Relations.Add(relation_vacation);
ds.Relations.Add(relation_sick);

// pass the data
mailMerge1.MergeBlocks(ds);
mailMerge1.Merge(ds.Tables["general"], true);