Como forma de resposta, para mim, é possível sim. Na interrogativa também é possível, e se alguém pergunta "Have you just done your homework?", com certeza algum tipo de resposta deve ser produzida, e a partir daí, podemos ter "No, I haven't just done my homework."
=> What are you writing now, or what have you just finished? I have just completed two books: a sixth fostering memoir.
=> And no, I haven't just been busted, it's been over 18 months since my last lot of involuntary taxation.
Actions completed in the very recent past (+just).
A. Have you just finished work?
B. I have just eaten.
C. We have just seen her.
D. Has he just left?