Hi,
If you are performing a multiple channel acquisition, the easiest way to write all of your data to a file and have new data appended to that same file will be to use the "Write to LabVIEW Measurement File" Express VI. This VI is located on the Functions>>Output Palette.
If you put one of these on the block diagram, a dialog box will appear with options including an "append to file" option. This Express VI also allows to configure how your channels are saved in the file and the LabVIEW Measurement File can be opened in Microsoft Excel.
There are some other vi's for writing data to a file on the Funcions>>All Functions>>File I/O palette. The "Write to Spreadsheet File.vi" on this palette will work for your application as well. There is an "append to file" input in which you will have to wire in a "true" constant to append your data.
I hope you find this information helpful.
Regards,
Hal L.
