How to add a custom field (not module) to Global Search

[marygriffen]

We have a custom field in the Projects module that we want to be able to use in the Global Search. I know that you can edit vardefs for the module to add a field to the search from the projects table, but where can we add a custom field from the projects_cstm table? (NOTE: we are using Crystal Professional v4.5.1b.)