How to add a calculated field to a report

In the report designer, select the Field List for collectionDataSource1
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Right click any field in the field list and select
Add Calculated Field

Right click any field in collection data source and select Edit Calculated Fields
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Edit the properties for your calculated field.
Make sure to set the Data Source to be collectionDataSource1
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Click Into the Expression Editor to set the expression for the calculated field09Capture

Now you should be able to use your calculated field as a normal field on your report