test.cs

private void textControl1_SubTextPartEntered(object sender, 
                                             TXTextControl.SubTextPartEventArgs e)
{
    // is the SubTextPart a valid merge block?
    if (DataSourceManager.IsMergeBlock(e.SubTextPart))
    {
        // set the merge block as the new internal master table
        if(dsManager.DataTables.Contains(e.SubTextPart.Name.Remove(0, 5)))
            dsManager.MasterDataTableInfo = 
            dsManager.DataTables[e.SubTextPart.Name.Remove(0,5)];
    }
}

private void textControl1_SubTextPartLeft(object sender, 
                                          TXTextControl.SubTextPartEventArgs e)
{
    // set the master table back to the originally selected table
    dsManager.MasterDataTableInfo = cbMasterTable.SelectedItem as DataTableInfo;
}