Is there a way to dynamically change the Save As file name from the default Chart.xls?
The default filename of Chart.xls in the Save As dialog box is hard-coded. If you wanted a different one, you would have to implement your own button that gets tag history using system.tag.queryTagHistory() and the start/end date properties of the chart, and then system.dataset.exportExcel() to export that dataset to an Excel file.