You could use VBA
Private Sub Worksheet_Change(ByVal Target As Range)
Const WS_RANGE As String = "A2" '<== this is the cell on action_plan _
with the dropdown, change to suit
On Error GoTo ws_exit
Application.EnableEvents = False
If Not Intersect(Target, Me.Range("C9")) Is Nothing Then
With Worksheets("Data_dump")
.Cells(Application.Match(Me.Range(WS_RANGE), .Columns(1), 0),
"J").Value = _
Me.Range("C9").Value
End With
End If
ws_exit:
Application.EnableEvents = True
End Sub
'This is worksheet event code, which means that it needs to be
'placed in the appropriate worksheet code module, not a standard
'code module. To do this, right-click on the sheet tab, select
'the View Code option from the menu, and paste the code in.
This assumes the student names are in column 1 of Data_dump

Signature
---
HTH
Bob
(there's no email, no snail mail, but somewhere should be gmail in my addy)
> Hi, I have a worksheet called Data_dump which contains my students
> results for their last 6 exams.
[quoted text clipped - 25 lines]
> Thanks in advance for any help
> Helen