To launch an external application, you can use the LaunchExecutableEx function. This function runs a program and returns without waiting for the program to exit. There is an example that ships with LabWindows™/CVI™ where you can check how to use the function mentioned before. The example can be found in Help >> Find Examples... >> Communicating with External Applications >> Operating Systems >> launchexe.cws.
Another option is using the ShellExecuteEx() function available in the Windows SDK. For more information on interfacing with the Win32 API, you can read the article Using the Win32 API in LabWindows™/CVI™