Logical expression SSRS

HI Experts,

I have written simple IIF expression to get category values but it is summing everything and placing in single cell it is not separating based on expression 

I was grouping by TaskNumber

=IIF(LEFT(Fields!StatusReasonReportingLabel.Value,8)="+Prepare",Sum(Fields!TaskStatusSecondsDuration.Value),0)




=IIF(Fields!StatusReasonReportingLabel.Value="+Travel",Sum(Fields!TaskStatusSecondsDuration.Value),0)



=IIF(Fields!StatusReasonReportingLabel.Value="+On Site",Sum(Fields!TaskStatusSecondsDuration.Value),0)

Can I anyone tell me where I was doing mistake please