Welcome, EmilyandCathy! Unfortunately, I'm pretty sure the answer to your question is no. Once the sperm is thawed it only lives for approximately 12-24 hours, and I *think* that's inside the reproductive tract. Even fresh sperm, which has a longer lifespan than frozen, only lives a short amount of time outside the body. I know that DesertSunsets, from the QP&P room, used a mircoscope to examine sperm leftover in the catheter something like 18+ hours after the insemination, and she and her DP found some that were still alive and swimming, but I seriously doubt there would be enough. You'd end up with a lot of dead and dying spermies and a possible health risk. You also would be cutting down on the sperm count by halving your sample, and you want as many little swimmers in there as possible. If you are really set on multiple insemination, the best bet is to buy multiple vials. Are you doing ICIs or IUIs?
Btw, why don't you come over and join us in the Queer Conceptions February thread? It's a great group of gals, and we'd be happy to answer questions/give you and your partner support.