I'm using an older version. I don't know about onProgressCallback.
It's maybe a progress bar between then addOneMoreAddress? Here is a
code on how I create a tsp object:
tsp = new BpTspSolver ( gmap2, directionsPanel, travelMode,
reasons ); // Create the tsp object
tsp.startOver();
for ( i=0;i<address.length;i++) {
tsp.addAddress ( address, addOneMoreAddress );
}
tsp.solveFinal ( tsp.getWaypoints (), callback );
function callback () {
gebDirections = tsp.getGDirections();
Polyline = gebDirections.getPolyline();
Duration = gebDirections.getDuration().seconds;
Distance = gebDirections.getDistance().meters;