If you really want an app to send an action listed in your Memos (Project) to Task (where you have your NA), there're several third party apps. I think there was Slap or similar.
If you just want to link the NA in Task to a Project in your Memos app, you can use PsLink. With PsLink, you can add the Project in the NA, then click on the Project to take you to Memos to view the Project details.
There are many apps available to customize Palm OS. But I second the suggestion to work with vanilla Palm apps first.