[MichaelCrawford]

Yes, there are all kinds of ways to do that.

But typically you see stuff like:

for ( i = 1; i < 10; ++i ){ DoSomethingUseful( i ); DeterminateProgress( i, 10 ); }

So each iteration of the loop, the bar advances by one-tenth its maximum length, without regard to what DoSomethingUseful actually does.

Chalk it up to lazy coders and tight-fisted bean counters.