Thanks Tom...

I already tried the expression u mentioned but i got the error as :

The Value expression for the textbox txtCRTotal refers to more than one report item. An expression in a page header or footer can refer to only one report item.

The expression I tried is :

SUM(IIF ( ReportItems!txtNoOfItems30.Value < 0 ,ReportItems!txtNoOfITems30.value , 0))

I used the above expression in the page footer.

The report executes well if I pass numerics as iif result sets.