How to stop Maps dimmingauto lock iPhone

Hi there, I just got the iphone4 and love the maps but there is one flaw. I connect to my work exchange server and the company policy is that it need to lock every every 5mins max. Now unfortunately this also happens when I am navigating. I cant change the company policy but I used to use google maps on my old blackberry and there was an option where you can tell the device not to go sleep if navigating (haha makes sense for the driver too), is there a similar function on the iphone4? Alternatively the blackberry also used to have an app that can control the dimming and autosleep of the device, is there something similar for the iPhone4?
Hope there is something as it would be greatly disappointing if there wasnt and I guess that would also make me doubt if it would be worth purchasing a navigating software as i dont want it doing the same thing while I navigate, would be a waste of money.
thanks for your help in advance
Noe
Message was edited by: nOe
iPhone 4 32GB Windows 7