This area in the LeapFrog / Relocation dialog box (Insert | Alignment | Leapfrog) enables you to specify the measurement routine file to use as the datum program file. This box becomes enabled when you click the Measure Datum Features option. You can type the full pathway to the measurement routine (.PRG) file, or you can use the Browse button to navigate through your directory structure and select one that way.
Once you select a file, the features available for use in the Leapfrog operation appear in the Available list.