The "fix" in the XYYY command to take account of a varying number of rows introduced a bug that often leads to one of two Excel error messages (error codes 9 or 13), and you won't get a plot. To get a fixed Add-In:
Start Excel.
In Excel 2003 and earlier versions, select Tools>AddIns and uncheck the "DPlot Interface" box.
In Excel 2007, click the Office button in the upper left corner. Click the "Excel Options" button. In the left pane click Add-Ins. At the bottom of the screen select "Excel Add-Ins" in the Manage box and click Go. Uncheck the "DPlot Interface" box.
Click OK and exit Excel.
Download the updated Add-In and save to %APPDATA%\Microsoft\Addins, overwriting the old version. If your browser doesn't accept %APPDATA% as a valid destination, on Windows 2000 and XP US English editions that is a shortcut to c:\Documents and Settings\<username>\Application Data. On Windows Vista it will generally point to c:\Users\<username>\AppData\Roaming.
Restart Excel and perform the inverse of step 1: bring up the Add-Ins dialog, check the "DPlot Interface" box, and click OK.
The next release of DPlot will include the same fix mentioned in this thread, but if that's not working for you then something is amiss. Excel is a little strange about giving up old Add-Ins; that was the main reason for the instructions about disabling the old Add-In before copying the new one. If Excel was running at the time you copied that file to your hard disk then there's no way it will work correctly. If you check the date of %APPDATA%\Microsoft\Addins\dplotlib.xla and it is older than 9/30/2008, then something went wrong. Another problem might be that you have multiple copies of the AddIn. If you look at Tools>Addins and see more than one "DPlot Interface" then you have more than one copy and will need to search your hard disk for dplotlib.xla, deleting all of 'em and repeating the previous instructions.
And if you aren't using the XYYY command then we're talking about completely different things - in that case please let me know what AddIn command you're using and what error message you're getting.
