how to show a datekey values greater than a particular datekey of a table in ssrs report

Hi,

I am doing the below but getting some weired result

=IIf(Sum(Fields!DateKey.Value, "DataSet2")> ReportItems!Textbox1.Value,Sum(Fields!DateKey.Value, "DataSet2"),Nothing)

textbox1 has the datekey ans datatset2 has all datekeys and then i am comparing

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simanta