Dear Ninja,
my boyfriend is coming home early and yes im happy about that but I will need his sperm a week after he leaves... what should i do?
~Wicked
Dear Wicked,
The saving of the sperm requires you to do a little prepwork, and a blow job (at the very least, a hand job).
First, you will need a specimen cup for his baby batter. If he's aware of the need to save his spunk, you can just have him jack off into the cup while watching a porn. If you're doing it incognito, it requires you doing the work for the squirt.
If you choose the blow job option, don't let him cum in your mouth. The saliva will start breaking down the sperm. Have him shoot on your chest, face, whatever, and scoop up your sample and put it in the jar. (if you can't find a jar, just put it in an ice tray. Depending on your purpose for needing it, that might be an easier insertion later.)
Good Luck!