'Doesn't work' is as much use as a chocolate fireguard.
Please explain in detail exactly what you have entered into the afterupdate event.
Do not retype it, copy and paste all of the code with code tags by using the # icon when making the post.
Alternatively upload your DB, zip it if it is too big to do as a accdb.
I did exactly what Bob Fitz said:
You need to put the code into the events procedure.
So, click the arrow down and select
Event Procedure.
Then click the button next to the down button with the three dots ...
This will open the forms code module.
Enter the code given earlier, immediately above the line that says
End Sub
Code:
Private Sub Combo284_AfterUpdate()
Me.frm_Marketing_Subform.Requery
End Sub
or
Code:
Private Sub Combo284_AfterUpdate()
Me.frm_Marketing_Subform.Form.Combo284.Requery
End Sub