First, you should add the dt to the waveform data if it's going to make any sense at all. Then you can modify the Express VI or use one of the other functions such as Export Waveforms to Spreadsheet File or the regular Write to Spreadsheet File. If you use the regular Write to Spreadsheet File, you'll have to build an array of timestamps like with WDT Get Waveform Time Array and convert both the timestamps and data to strings. Look at the diagram of Export Waveform to Spreadsheet File. That's a lot easier to modify than the Express VI.