I think you can do that when I went for
SCJA exam
I was given erasable notepad, lady said start exam
I said can I take practice
test (it was not related to
java but to introduce you how to give multiple choice exam on computer).
It was of about 15 minutes test so you can use that time.
But the problem is if it is erasable pad and you use too much of space
than you will not get space for rough work especially for flow control question and etc.