Excel VSTO how to check if the Cancel button has been triggered from the dialog after the WorkbookBeforeClose event is fired?

I am currently developping an Excel VSTO addin and here is the code for WorkbookBeforeClose

private void App_WorkbookBeforeClose(Excel.Workbook Wb, ref bool Cancel)
    {
        bool isEnabled = false;
        setRibbonControlState(ref isEnabled);
    }

In this code I disable the ribbon if there is no workbook left opened. But if I press the Cancel button from the dialog after I tried to close Excel, the ribbon gets disabled anyway. But as the WorkbookBeforeClose event passed a Cancel parameter, I don't know how to set that parameter when I press the button, how do I check the dialog prompted for the button that has been triggered.

All cases I have seen so far implement a dialog in the body of the WorkbookBeforeClose handler, but I don't want to implement a custom dialog, I would like to use the one provided by default.

Thanks!