if you mean something like this:
http://www.amazon.com/Insten-Ethernet-Splitter-Connector-Adapter/dp/B003C2QS90
then no, it wont do it.
Long long ago, the grand idea (tm) behind said splitter was, once upon time, during time of cat5, that ethernet used only TWO of four pairs for network traffic, said splitter, if put on both ends, would allow you to use said one cable as two. (with separate cables on both ends) by using two pairs for each connection.
It is far from optimal though and using just one would NOT work, they should ALWAYS be used in pairs.
That was the idea back in cat5 time though, now with cat6, you are using all 4 pairs and.. this does nothing except as said, allows you to permanently wire TWO things at once and have only...