ssrs 2008 use parameter value to work with row visibility

In an ssrs 2008 report, I would like to add logic that looks the following for determining if a row is visible are not.The logic is the following =iif(Fields!MILESTONE_CODE.Value = "015", false, true)However I would like to expand this logic out for a user to be able to select one or multiple milestone values based upon a parameter to be setup called pmilestone.The milestone values will look like:"005" for 5 days,"010" for 10 days,"015" for 15 days, and"020" for 20 days.Thus could you show me the ssrs code that will accomplish the row visibility logic I am looking for? In addition, would you show me how to setup the corresponding parameter logic so the row visibility logic will work?