Excel Services - Edit .xlsx with external data

I created a new .xlsx file in Excel 2013 with external data connection to MS SQL database. Uploaded it to SharePoint Server 2010 document library.

I edit this file in workflow action. It uses ExcelService class generated via web reference. Here is my code:

// string SheetName = "Sheet1"
// string CellName = "C1"
// string Variable = "10"
using (var xl = new ExcelWebService.ExcelService())
{
    xl.Url = "http://localhost/_vti_bin/excelservice.asmx";
    ExcelWebService.Status[] status;
    string sessionId = xl.OpenWorkbookForEditing(url, CurrentCulture, CurrentCulture, out status);
    try
    {
        xl.SetCellA1(sessionId, SheetName, CellName, Variable);
        xl.SaveWorkbook(sessionId);
    }
    catch (System.Web.Services.Protocols.SoapException)
    {
        throw;
    }
    finally
    {
        xl.CloseWorkbook(sessionId);
    }
}

I get this exception every time when I run my code to edit any cell in the document:

System.Web.Services.Protocols.SoapException: This workbook cannot be edited because it contains the following features:

• External data ranges (also called query tables)

To edit this workbook, open the workbook for viewing, select Save a Copy from the File tab, and edit the new copy. 
   at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) 
   at System.Web.Services.Protocols.SoapHttpClientProtocol ExcelSetCellValue.Invoke(String methodName, Object[] parameters) 
   at ...ExcelService.OpenWorkbookForEditing(String workbookPath, String uiCultureName, String dataCultureName, Status[]& status) 

Method GetCellA1 works fine.

Can I edit Excel document with external data in SQL database using Excel Web Services?

The cake is a lie.