You need to set up a self relationship. Let's say your table is called ENROL and the calculated field you set up is called NameKey. You also need to set up a global text field that we will call NameKeySelect - this will be the field on the layout with the drop down pick list.
You need two table occurrences of the ENROL table on your relationship graph - let's call them ENROL and ENROL_byNameKey. Create a relationship thus:
ENROL::NameKeySelect = ENROL_byNameKey::NameKey
So the user selects a name using the global field pick list and then the script that runs will be a simple Go to Related Record using the relationship above and going to whatever layout you choose. The script can either be triggered by clicking a button or OnObjectModify for the field (if you are using FileMaker Pro 10).
See how that works?