LabVIEW provides some NI-SCOPE examples, which you can use for quick development. Below is a modified version of the example niSxope EX Fetch Forever.vi. It uses an external signal on VAL_PFI_1 as a start trigger.
Note: This image is a LabVIEW snippet, which includes LabVIEW code that you can reuse in your project. To use a snippet, right-click the image, save it to your computer, and drag the file onto your LabVIEW diagram.