Thies,

In addition to Tom and others' ideas, have you thought about turning off
screen refreshing until your code completes?

Off the top of my head, you can use 'delayScreenUpdates(yes)' at the beginning
of your code, do all the processing, and then invoke 'delayScreenUpdates(no)'
afterwards.  This is supposed to stop the UI from rebuilding the screen for
lots of intermediate changes. 

HTH, 
Jim Moseley