Not sure what your goal is by transfering to Excel... Be aware that if you have built an inclusive WBS, as it is intended, you may have reference errors, embedded nightmares and so on when transfering. You may only be able to capture a stagnate picture, not a fluid, constantly up to date reflection of what is taking place in your WBS. Project does that for you. Whatever it is that you are trying to do in Excel may be a function easily done in Project - or - imported into your milestone agenda/expenditure analysis, your manhour overview or your cost/schedule/perfomance overview...
So, there you go...