Use the Not a Path value as the default value for a path control, so you can detect when the user fails to provide a path and display a file dialog box with options for selecting a path. Use the File Dialog function located on the Functions»File I/O»Advanced File Functions palette to display a file dialog box. The Path symbol in the control or indicator changes to the Not a Path symbol
and Not a Path appears in the text field to indicate the path is invalid.
Complete the following steps to change the value of a path control from an invalid path to valid path.
Complete the following steps to change the value of a path control from a valid path to an invalid path.