Updated 31.05.2016...
Thanks for your help. I found the following solution:
foreach (MSExcel.WorkbookConnection cnn in wb.Connections)
{
if (cnn.Type.ToString() == "xlConnectionTypeODBC")
{
cnn.ODBCConnection.BackgroundQuery = false;
}
else
{
cnn.OLEDBConnection.BackgroundQuery = false;
}
}
Frank