Thank you for your post.
I am assuming you have a table that includes the Event Title and EventID. For this example, let's assume the table is called "LOOKUP".
In your main table (which I'll call MAIN), create a relationship into LOOKUP based on EventID, and create a relationship to a second table occurrence of LOOKUP (LOOKUP 2) based on Event Title.
Next, in MAIN, double-click on the Event Title field definition to bring up the Options dialog box. Select the "Auto-Enter" tab and put a check mark in the option "Looked-up value". Starting with table "MAIN", Lookup from related table LOOKUP, and copy value from field "Event Title".
Double-click on the EventID field, and put a check mark in the option "Looked-up value". Starting with table "MAIN", Lookup from related table LOOKUP 2, and copy value from field "EventID".
Now, go to browse and enter an EventID, and the corresponding Event Title will display. Go to a new record, enter the Event Title, and the corresponding EventID will display.
If you need clarification for any of the above steps, please let me know.