There are two virtual dialpads on the Droid. If I open the Phone app, I immediately see a gray dialpad. At the bottom right of this dialpad, there is a back arrow that enables me to make corrections to numbers that I enter.
If I go to the Call Log or Contacts and dial a number by selecting an entry, I get a dialing status screen. At the bottom right of this screen is a button to access a dialpad. When I hit this button, I get a green dialpad that does NOT have a back button. Nor is a back button available via the Menu. So if I am typing in an additional number (say, a prescription number for a pharmacy), and I make an error, I must cancel the call & redial.
This is a baffling and annoying inconsistency in the interface.