you can use the males from another plant and cross it,,,or use the males from the plant you grow the pumpkin on. wich is called selfing a plant. So only need one plant.
The night before the female opens you tie her shut,,so she cant open..or cover her up(ziplock bag,or pantyhose). so the bees cant get to it. You tie up the male flowers to.
Then on the morning they open you rube the male genitalia over the female parts, After this you tie the female shut again. No bees allowed in there. Then you sit back and smoke a sigaret, you just had pumpkin sex. It wil either start growing wich you wil see in a few days..or grow just a bit,and then abort.