Yes you can enter more than one number > where it says 'phone' to enter their number... click on it... it will bring up a list of labels that you can select from to enter more numbers... i.e. work, home, office, blah blah blah. hope this helps.
when you are editing under their contact name there is a green + symbol to the right of where it says phone, hit that and it should bring up another "phone" line that you can put a different # in for that person and label it "home", "work" or whatever.
Ok, I will try that again. I've done that, but each time it over-wrote the previous number. Then, when I hit the person's name, only one number comes up. But, I will take another run at it. Cover me.
Another possibility, assuming you're using gmail, is to use the gmail contacts interface on your computer to edit your contacts and add multiple numbers. They will then be synced with your phone.