Progress bar troubles

Is there any way to update OnGUI() from, say, within a for loop in Update()?
I have a script that lays out a generated scene. This is dealt with just the one time, and as a result, any progress bar i create inside OnGUI() only displays once the job is done.
Is there any way I can force display of the Rect() while the environment generator's for loop is being worked on?

 

Not to worry.
Replaced the for loop with an if and all is well.