I don't believe it is possible to increase or decrease the speed of execution highlighting.
But, other techniques are available. I will briefly list some of the possibilities I have used when I found myself in situation where I wanted to control the highlighting speed.
Increase speed:
Use break points to allow the code to run quickly up to the point you are interested in. Then go to execution highlighting. Remeber to remove break point when done!
Use arrays built at the edge of loops as temporary "logs" of intersting values.
Include conditional checks that only execute after a specific number of iterations to let you skip thru a number of iterations, and then set execution highlighting.
Decrease speed:
Use single stepping.
Use one button dialog to stop where you want.
Ben