停止div行到包装器中的下一行

So I have a row of divs 3 infact which all float left and have equal amounts of margin between, however when it comes to the 3rd or right hand one if I put too much margin it forces it down to the next line naturally. I want it to sit slush within the wrapper so there is equal amounts is space between each one...So I have a row of divs 3 infact which all floa