Unfortunately it can't be changed. You could use the HTC Home Plugin instead. It has a lot more features and shows your call history. You can download the HTC Home Customizer from here, which will automatically download the HTC Home Plugin for you.
http://www.pocketemu.com/page.php?2
Or you could try something like rlToday. If you look around the forum you might even find a skin that looks like HTC Plus. The skins are customizable, so you could change them to suit your needs or create your own:
http://rotlaus-software.de/projects/rltoday/