I have a Gigabyte 990fx....UD3 board and it auto detects 3 or 4 pin connections, so I just used a standard splitter that plugs into the board with three pins. (3 pin connections with one connection that only has two IIRC)
I would expect it to do the same with your board.
So you just use a 3 pin fan splitter (like this one: http://www.newegg.com/Product/Product.aspx?Item=N82E16812119148)?
How do you plug it in to the mobo's 4 pin CPU fan header?