In the on_current event procedure which I outlined previously you could set the fields to locked, as follows:
Private Sub Form_Current()
If Me.Dirty = True Then
MsgBox "This record is being edited, you cannot update this record."
[field1].locked = True
[field1].locked = True
[field1].locked = True
'...etc I don't think you can lock the whole form so you have to lock the individual fields
else
[field1].locked = False 'this unlocks the field if not being worked on
[field1].locked = False
[field1].locked = False
End If
End Sub
Good Luck
Rick