Invalid use of "Null"

[ceesql]

I have Access 97 App, that, until July, has worked fine. July 1 the subj error started appearing. Unable to de-bug - hitting blank. I've located the field which is null (ptdEnd) but unable to locate where this field is being updated. I documented the report form and discovered that the row source for the field displayed also shows a different format for July. See below.

I'd appreciate any help. Thanks

Dim M As String
Dim Y As String
Dim YMO As String
Dim Y12 As String
Dim ptdBeg As String
Dim ptdEnd As String
Dim pptdBeg As String
Dim pptdEnd As String
Dim B As String
Dim RptName1 As String

M = "Y" & Mid$(Me.cmbM_date_choice, 3, 2) & "M" & Mid(Me.cmbM_date_choice, 6, 2)
Y = "Y" & Mid$(Me.cmbY_date_choice.Column(0), 3, 2)
YMO = "M" & Mid$(Me.cmbY_date_choice.Column(0), 6, 2)
Y12 = Me.cmbY1vsY2_date_choice
ptdBeg = "Y" & Mid$(Me.cmbPTDbeg_date_choice.Column(0), 3, 2) & "M" & Mid$(Me.cmbPTDbeg_date_choice.Column(0), 6, 2)
ptdEnd = "Y" & Mid$(Me.cmbPTDend_date_choice.Column(0), 3, 2) & "M" & Mid$(Me.cmbPTDend_date_choice.Column(0), 6, 2)
pptdBeg = "Y" & Mid$(Me.cmbPPTDbeg_date_choice.Column(0), 3, 2) & "M" & Mid$(Me.cmbPPTDbeg_date_choice.Column(0), 6, 2)
pptdEnd = "Y" & Mid$(Me.cmbPPTDend_date_choice.Column(0), 3, 2) & "M" & Mid$(Me.cmbPPTDend_date_choice.Column(0), 6, 2)
RptName1 = "rpt" & Left(Me.cmbChooseReport.Value, 9)
B = GetBrokeredClause(Me.chkBrokered.Value, Me.chkkDistributed.Value)

Combo Box: cmbPTDend_date_choice
After Update: [Event Procedure] AllowAutoCorrect: True
Auto Expand: True Back Color: 16777215
Back Style: Normal Border Color: 0
Border Line Style: Solid Border Style: First Page
Border Width: Hairline Bound Column: 1
Column Count: 2 Column Heads: False
Column Widths: 0;1440 ColumnHidden: False
ColumnOrder: Default ColumnWidth: Default
Control Source: p1_end_yr_mo ControlType: 111
Decimal Places: Auto Display When: Always
Enabled: True Event Proc Prefix: cmbPTDend_date_choice
Font Bold: No Font Italic: False
Font Name: Times New Roman Font Size: 10
Font Underline: False Font Weight: Normal
ForeColor: 0 Height: 360
HelpContextId: 0 Left: 5160
Limit To List: True List Rows: 8
List Width: 0 Locked: False
Name: cmbPTDend_date_choice Row Source Type: Value List
Row Source: 2000 01 Jan;"2000 Jan";2000 02
Feb;"2000 Feb";2000 03 Mar;"2000
Mar";2000 04 Apr;"2000 Apr";2000 05
May;"2000 May";2000 06 Jun;"2000
Jun";2000 07 Jul;"2000 Jul";2000 08
Aug;"2000 Aug";2000 09 Sep;"2000
Sep";2000 10 Oct;"2000 Oct";2000 11
Nov;"2000 Nov";2000 12 Dec;"2000
Dec";2001 01 Jan;"2001 Jan";2001 02
Feb;"2001 Feb";2001 03 Mar;"2001
Mar";2001 04 Apr;"2001 Apr";2001 05
May;"2001 May";2001 06 Jun;"2001
Jun";2001 07 Jul;"2001 Jul";2001 08
Aug;"2001 Aug";2001 09 Sep;"2001
Sep";2001 10 Oct;"2001 Oct";2001 11
Nov;"2001 Nov";2001 12 Dec;"2001
Dec";2002 01 Jan;"2002 Jan";2002 02
Feb;"2002 Feb";2002 03 Mar;"2002
Mar";2002 04 Apr;"2002 Apr";2002 05
May;"2002 May";2002 06 Jun;"2002 Section: 0
Jun";2002 07 July;"2002 Jul";2002 08
Aug;"2002 Aug";2002 09 Sep;"2002
Sep";2002 10 Oct;"2002 Oct";2002 11
Nov;"2002 Nov";2002 12 Dec;"2002
Dec"
Special Effect: Sunken TabIndex: 20
TabStop: False Text Align: General
Text Font Char Set: 0 Top: 3345
Visible: False Width: 1725

 

[TrojanRabbit]

Perhaps cmbPTDend_date_choice isn't getting data. How do have this field getting data?