It strikes me as odd that in today's day and age, people still have questions as too what it takes to get pregnant. I hope you do not take offense to that statement but honestly, if you do not know that the only way to get pregnant is to have seamen inside your vagina, then maybe you are not mature and or educated enough on the subject to actually be having sex in the first place. Honestly, how could you think you can get pregnant by having seamen on your leg? Unless he came on your cookie as opposed to inside it, then there could be a chance, however slight of a chance it is.
Finally to answer your question...
You can not get pregnant from having seamen on your leg.