Updating a form field based on previous field

Couldn't find this one in the archives and I am very VBA illiterate... borderline dumb... but, here goes:

I have a form that, when data is entered into one field, I would like to automatically populate the very next field based on a secondary table. For instance, when the TECH_ID is entered, upon exiting (or whatever action), I would like the current record's TECH_NAME to be populated (data located in the EMPLOYEE_TABLE). I currently have an update query working this, but would like to keep the update live on the form.

any help would be greatly appreciated my people.