Help with training my cat to stay down! please help?

I am going to have a baby soon and almost have my nursery done. I leave the door open and my cat will go in there and jump on the stroller box to look out the window but she also has been jumping in the crib. I tried to put things in the crib to keep her out of it but she still wiggles her way between things to sit on the crib mattress. I take her out of the crib everytime I hear her jump in it and give her a firm no. I tried closing the door but she makes this god awful meow and will bang on the door and honestly I can't stand it and just want to rest! Any ideas on how to train her to stay out of the crib? I don't want to worry about her jumping on the baby when he gets here!