I guess this is enhancement request.
When I write to existing excel file I would to preserve its structure. Here is an example: I have worksheets called "Sheet1" and "Sheet2". If I write to "Sheet1" and deselect option "Append to File (if exists)" I am going to lose "Sheet2". If I write to "Sheet1" and select Append to File (if exists)" my value will be appended to whatever I have on "Sheet1", while I would like to overwrite "Sheet1" with new values.
Please let me know if it is possible.