When you have drawn a wall, you can still edit that wall.
All you have to do is to double click on the wall that has been placed down and this box will appear again:
You can then start to change the settings of that individual wall.
All you have to do is change whatever settings you want and then select ok, then the wall will be changed.
We're not around right now. But you can send us an email and we'll get back to you, asap.