Changing a will

Just thought I would throw this question out here as surely everyone interested in this forum has made out their wills! :o)

Does anyone know if once you have had a lawyer do your will and you have had it notarized, is it possible to go back and make a change to it (a codicile?) yourself and have that notarized and place it with the original will.
Hope this makes sense. When my husband and I got married we moved into my house which is in my name. We made out our wills and we agreed that the house would be left to my two children which was stated in my will. We just had our mortgage refinanced and the house is in both our names. We do want to be sure that the house still goes to my children in the event that I die first. He wanted to change his will to specify that the house would go to my children when he died. Does anyone know if this can be done without having to have his will redone?