It's difficult to provide specific advise without seeing some sample data in a Tableau Packaged Workbook. However, I would suggest you could try to create a calculated field as follows: [PackageId] != [ShellId]
This field will return true if the two fields don't match. Thus, you can just throw that field on the filter shelf and set it to true.
if packageid=shellid then "hide" else "show" end
put this on filter shelf with values set to show