The UpdateProgressBar method updates progress in a popup window shown by ShowProgressBar method with percentage in percent parameter.

 app.UpdateProgressBar( percent );

See also: ShowProgressBar, HideProgressBar

function OnStart()
{
  app.ShowProgressBar( "Processing...", 0 );
  setTimeout( "app.UpdateProgressBar(25)", 1000 );
  setTimeout( "app.UpdateProgressBar(50)", 2000 );
  setTimeout( "app.UpdateProgressBar(75)", 3000 );
  setTimeout( "app.UpdateProgressBar(100)", 4000 );
  setTimeout( "app.HideProgressBar()", 4100 );
}