The only way you can do this is to write it to a spreadsheet file and give it the extension .csv or .xls so that excel will open it directly, otherwise just write it to excel but do not make it visible.
You can also use the write to "spreadsheet file.vi" and set the append parameter to false. If you specify a file that already exists, a dialog box will appear asking if you want to overwrite. Saying yes will overwrite the file. This process will allow you to replace an excel file without ever having opened excel.