I am not sure why you just don't use "Me.FName" to reference the field. Me refers to the report, and FName refers to the control or field, and Me.FName returns the data currently in the control. What I do is to put the fields on the report, and then just set their visible property to No. Then I don't have any problems referencing them, and they are not shown to the user.
Alternatively, seeing as it looks like you are trying to concatenate text fields into something like "Smith, John, Jr." why don't you do this in an underlying query by adding a field like this to a query that pulls all your data from tbl:
FullName:([LName] & ", " & [FName] & ", " & [Suffix])
The results in the query will be "Smith, John, Jr." and you can just drop this field onto your report - after you make the query the record source for the report.