Modules & VBA :: Tracking Form - Code Does Not Review All Subform Records

I'm having some problems with VBA code I'm writing that references a subform. I'm pretty new to VBA and am not sure what the problem could be. The parent form (TrackingForm) tracks dates different tasks were completed. The subform (Child2) tracks exceptions that also need to be marked completed. I need ALL dates to be marked as completed before the entire tracking record can be marked as completed.

I have the following code entered into the OnFocus event of the tracking records Me.Completed_Date field:

Private Sub Completed_Date_GotFocus()
If IsNull(Closing_Date) Or IsNull(Package_Received) _
Or IsNull(Upload_By) Or IsNull(Initial_Review_Date) _
Or IsNull(Me.Child2.Form![Date Exception Completed]) Then
Me.Completed_Date.Locked = True
MsgBox "Completed Date cannot be entered - outstanding items.", vbOKOnly, "Warning!"
Else: Me.Completed_Date.Locked = False
End If
End Sub

What ends up happening is that, if there is more than one exception record on Child2, the code only seems to care if one of the records (usually the first record) has something entered in the [Date Exception Completed] field. I can't seem to make it look at any successive records in Child2 to ensure they are also completed prior to unlocking the Me.Date_Completed field. I have googled this extensively over the last day and the only response that seems to recur involves using a Recordset function that I have never used and am unsure how to.