Yes, if you have one of your daughters named as the executor of your Will you can add your second daughter as a co-executor of your Will with the other daughter without having to re-write your Will.To do the above, you need to sign an addendum to the Will naming the one daughter as the executor referencing the first Will and specifically stating that both of the daughters will be co-executors.I suggest that you have a Wills and trust attorney assist you with this addendum.