The Start Label box in the Iterative Alignment dialog box (Insert | Alignment | New | Iterative button) allows you to define a label that PC-DMIS execution moves to when remeasuring iterative alignment features. It remains disabled until you mark the Meas All Always check box.
For information on how the Start Label works with Meas All Always during execution, see the "Meas All Always" topic.
For more information on labels, see "Using Labels" in the "Branching by Using Flow Control" chapter.