Max from parameter value.

Hi, i have a question, how to return the max value from values which where passed from parameter?I have query: =Switch(Fields!Wartosc.Value = Max(Wartosc.Value, "DataSet1"), "Red",Fields!Wartosc.Value = Min(Fields!Wartosc.Value, "DataSet1"), "Yellow")But it returns the max & min value from whole database. Not from few values which parameter passed.