force a string to 2 decimal places

i have a repeater item that displays a double. occasionally the double seems to be coming out with 3 decimal places like this 1165.833. im trying to force it to two decimal places by wrapping it in a string.format method but it still comes out the same:

<%# String.Format("{0:f2}",DataBinder.Eval(Container.DataItem, "pricerange").ToString())%>

any ideas why?