Okay. The cervix is actually a sort of passage from the vagina into the uterus. On average, the ectocervix or external os, the part that bulges into the vaginal passage, is 3 cm in length and roughly 2.5 cm wide. Past the external os is the cervical canal, which is maybe 4 cm long, and might make it to 8 mm in width, which is not very wide at all. This would be the hideous pain portion of the program, since the cervical canal is NOT designed to allow a penis to enter it. At the end of the cervical canal is the internal os and beyond that is the uterus itself.
Unless a woman is ovulating or menstruating, the external os is blocked by mucus designed to keep sperm out. During ovulation, the mucus thins to allow sperm to enter. Folds in the cervical canal hold sperm and release it into the uterus over several hours, to help increase the chances of fertilization. The whole purpose of the cervix is to keep most things out, except during ovulation, and even then, it's only sperm that should be going in.
Now, if you need these things to absolutely, positively happen for the sake of your story, come up with magic or some other method to transport the sperm in, because you are not going to be able to bend anatomy to your purposes unless you want to wreck the woman for life. You can't pick and choose what bits to keep, so either you're going to go with basic biology or you're going to embark on fantasy, Pick one, and have fun.