-----------       ------------           -------------    
|excel     |     |           |           |           |
|template  | <== | callback  |   <====   |database   |       
|          |     |           |           |___________|
|          |     |           |
---------        |___________|   <=====  -------------
                                         |            |
                                         |DCOM server |
                                         |            |
                                         --------------