In the COM version of ExcelWriter, when using the ExcelApplication object's Open method to modify an existing spreadsheet which is in BIFF8 format (Excel 97 and above), and which already contains charts and/or images, you cannot add additional charts or images in your script (using the Add method of the Charts object). This problem does not occur if the original spreadsheet is in BIFF7 format.

1. Place all the charts/images you will need in your original spreadsheet.
2. If you need to add charts/images dynamically at runtime, do not put any charts/images in the original file. Add them all with your script.
3. If you must have some charts/images in the original spreadsheet AND add some charts/images at runtime, save your original spreadhsheet in BIFF7 (Excel 95) format. You will then be able to add charts/images dynamically.
4. Rewrite your code to use the .NET version of ExcelApplication which does not have this limitation.