Unsaved "dot" in close button of Excel

Using AppleScript Studio, I have a main window and attach Finder’s open panel to it when I wish to open an Excel worksheet. My app then opens this worksheet in the background and does some extensive calculations. If I attempt to prematurely close my app’s main window or out-and-out quit my app, I then attach another panel in which I ask do I want to stop these calculations and save the intermediate result. If I do not, then these calculations continue. If I do want to stop and save, then I call:

tell application "Microsoft Excel" to save workbook

All the above works; however, what fails is the Unsaved “dot” remains when I just want to prematurely close my app’s main window. Only when I want to quit my app altogether, does the “dot” disappear. In both cases, the Excel spreadsheet is indeed saved (based on the time stamp) … it’s just the remaining Unsaved “dot” when closing the window that’s frustrating me.

Thanks in advance.