Well, I guess we tried but still no cigar...I changed my VBA to conform

Private Sub Aneurism_AfterUpdate()

If Me.Aneurism > 4 Then
   Forms![MRA Form_JPS]!Label113.BackColor = vbRed
   Else
   Forms![MRA Form_JPS]!Label113.BackColor = vbWhite
End If

End Sub

but nothing seemingly has been affected.

???

Yes, thanks lots, this works on the main form, but I wanted to show you the
current state of the VBA in that sub-form because it doesn't work quite as I
would've thought it could. You may be able to suss out the cunundrum by
perusing it (see below)

Option Compare Database
Option Explicit

Private Sub Aneurism_AfterUpdate()

  Call Form_Current

End Sub

Private Sub Form_BeforeUpdate(Cancel As Integer)

Me.[Aneurism] = Nz(DMax("[Aneurism]", "qry_Aneurism_JPS", "ID=" _
& Me.ID), 0) + 1

End Sub

Private Sub Form_Current()

   Dim lngColor As Long

   If Me.Aneurism > 4 Then
       lngColor = vbRed
   Else
       lngColor = vbWhite
   End If

   With Me.Parent!Label113
       If .BackColor <> lngColor Then
           .BackColor = lngColor
       End If
   End With
   
End Sub

Private Sub Form_AfterUpdate()

   Call Form_Current
   
End Sub

I think you'll probably agree that there's a need for a modification or two
or three.

Thanks in any event - it's an improvement.

I guess I should be less vague about how I think it will work: when the
threshold value of 4 is exceeded, I think the main form label should go red
and remain red until the offending record gets removed.

The other aspect of the behavior in this sub-form that I'm finding is
unexpected is as follows: if the user returns to the sub-form at a later
point and modifies an entry on one of the records, then the value of Aneurism
of that record is incremented, which I don't want happening. Is there a
workaround to that?

Thx!