SSRS sum values between dates

Hi all,

Im new to this forum so my apologies if this is listed in the wrong place. I am attempting to set up a report with a number of datasets. I want to include an expression that sums all values between particular dates within a dataset.

I have tried variations of sums and IIFs that have ultimately led to errors - this is my latest attempt.

=IIF(Fields!DateRaw.Value) BETWEEN 01/01/2013 AND 01/05/2013, sum(Fields!Net_Amount.Value) ,"City")

Not sure where I am going wrong - does the IIF need pointing to the dataset?

Error report:

The Value expression for the text box ‘Textbox5’ refers directly to the field ‘DateRaw’ without specifying a dataset aggregate.  When the report contains multiple datasets, field references outside of a data region must be contained within aggregate functions which specify a dataset scope.

Thanks in advance for your help.