If you have access to the LabVIEW Microsoft Report Generation Toolkit, you can find a much easier way to read/write (almost arbitrary) Excel Worksheets without using ActiveX at all! Given that even Microsoft seems to have abandoned ActiveX development/support (try getting ActiveX help in Windows 7, for example), going the Excel Report Object way seems the way to go.
Some comments. I posted in January of this year (look for Revised "Generate Excel Report" Example) some code that replaces the example that ships with LabVIEW. I've used Excel quite a bit with LabVIEW, and the new Report Object routines are a lot more User-Friendly than ActiveX!
For some reason, the NI "model" of Excel seems to be of a "write-only medium", i.e. a "Report". Thus there is no analog of "File Open", only "File Create". However, there is absolutely no problem opening an existing Excel file (with data), reading the data, writing new data (either appending rows to an existing Worksheet, rewriting/overwriting rows in the Worksheet, or creating new Worksheets and adding data) and then saving the file with the same name.
There are a few cautions to take, however. The current LabVIEW "model" of How We Work With Excel (i.e. the "Write-only" model) has a curious bug feature. Suppose you open an Excel Workbook and write out some data. You don't Save/Close the Workbook right away, but leave it open on the screen so you can examine what you wrote. Now, before you ask LabVIEW to Save the Excel file, you click on the red X in the upper right corner of your new Excel Workbook and close it. Now you exit LabVIEW. Surprise -- LabVIEW has deleted (!!) your newly-created Excel file!
As I noted, this is a "feature" built-in to the Report Save code (which I have brought to NI's attention). I've devised my own work-around to deal with this bug feature -- before I call the Report Generation "Save" or "Close" routine, I first test if there is an Active Workbook Object (meaning that the Workbook is still open and hasn't been closed "by hand") -- only then do I proceed to allow the Save and Close to occur.
Hmm. So how do I do this test? Time for the Dirty Little Secret -- I use the Excel Get ActiveX Reference (on the Excel Advanced Palette) and examine the Excel-._Application ActiveWorkbook property. If it is not an Empty Path, then it is safe to Save/Close the Workbook.
Bottom Line -- you can do quite a bit using the Report-Object tools LabVIEW provides in the Report Generation Toolkit without needing to use ActiveX except in rare instances. You can treat an Excel spreadsheet as a "file object" that you can read, write, and modify, without needing to worry about "templates" and without needing to adhere to a Write-only model of Report Generation. A little care is needed, but it is pretty easy to address individual Worksheets, individual rows/coluumns on a Sheet, entire blocks of data, etc.
Bob Schor
