Report Designer and referencing calculated field values in a formula

The data here for mailing labels is somewhat inconsistent, supplied and maintained by a 3rd party provider. I am trying to customize the mailing MailingLabels report to handle this data by populating up to four generic text boxes:

AddressLine1

The source table has five relevant fields:

NAME , MAILING1 , MAILING2 , MAILING3 , CITY_PROV , and POSTCODE  (I use the  NAME  field directly)

The inconsistency is that one or more of  MAILING2 , MAILING3 , and POSTCODE can be empty, so in these cases I want to skip them for that particular label.

I am using Report Designer's calculated fields (which I've named addr1, addr2, addr3, addr4) to set the value of each AddressLine text box. The logic for Address Lines 2 through 4 depends on the result of calculations from lines 1 thru 3. How can I reference the output of these other calculations for the same record in Report Designer?

I find using the calculation's name does not work (e.g. formula: addr1 <> BC.GIS_ADMIN.ASSESSMENTDATAPRIMARYVIEW.MAILING2 prints MAILING2's value twice on the label), and by using its TextBox name instead (e.g. AddressLine1), I just see value of MAILING1 and True  on the label.

Will someone please explain to me how to refer (in a calculated field's formula) to a value in an already-calculated report field for that record? Can it even be done? I hope I've made myself clear here :)

Thanks,