I noticed you're using the MS Office Report Express VI to generate your report. This Express VI is a "one stop shop" for editing documents. When the Express VI finishes executing, the document is saved. If you then run the Express VI a second time, it will create a new instance of the document template and edit that instance.
If you want to perform multiple edits on the same document, you will need to use the Report Generation VIs from the Report Generation palette. In particular, you could use the Append Report Text.vi and specify the appropriate bookmark(s) where you want to insert data with the "MS Office parameters" input to that VI.
Hope this helps,
-D
