Hello,
In order to save three columns into a spreadsheet file, I would recommend using two VIs that come in LabVIEW.
1) Create a 2 dimensional array by using build array and wiring in your three inputs. The "Build Array" Can be found under the 'Array' sub palette.
2) After creating a 2 dimensional array, you can write this to a spreadsheet file using the "Write to Spreadsheet file" VI. This VI can be found on the FILE I/O palette.
Additionally, National Instruments has a large amount of example programs that might be helpful. Here's a link to an example that might be close to your application:
Saving to a Spreadsheet FileHope this helps,
Robert Manion
Applications Engineering
National Instruments