PO Detail Subform Line Numbering Problem

[ChrisThomas99]

I'm pulling my hair out here I have a Purchase Order form the main form is from query from the PO header table and then a subform (for the line detail) from a query from the PO Detail table.
I have the following code in the "Before Update" event to add an incremental line number to each of the individual PO Lines. I Have this code working fine in the Sales order part of the Database but for some reason the same code is not working here:

Private Sub Form_BeforeUpdate(Cancel As Integer)
Dim strWhere As String
strWhere = "PONumber = """ & Me.Parent!PONumber & """"
Me!LineNumberID = Nz(DMax("LineNumberID", "tblPurchaseOrderDetail", strWhere), 0) + 1
End Sub

I'm getting the error: - Runtime error '3464' data Type Mismatch in criteria expression? I don't know why can anyone of you gurus help at all?

The LineNumberID field in the table tblPurchaseOrderDetail is of data type Number - Long Integer

The PONumber Field in both the Header and Detail Tables are again both defined as data type Number - Long Integer

Thanks

[pbaldy]

No delimiters for a numeric value:

http://access.mvps.org/access/general/gen0018.htm

[ChrisThomas99]

Thanks for that, complete novice here, checked the link it makes sense, but not a clue where to put the apostrophe's, I tried a couple of ways but just getting various different errors? Sorry...

[Missinglinq]

If PONumber is defined as a Number, the syntax would be

strWhere = "PONumber = " & Me.Parent!PONumber

If PONumber is defined as Text, the syntax would be

strWhere = "PONumber = '" & Me.Parent!PONumber & "'"

Linq ;0)>

[ChrisThomas99]

If PONumber is defined as a Number, the syntax would be

strWhere = "PONumber = " & Me.Parent!PONumber

If PONumber is defined as Text, the syntax would be

strWhere = "PONumber = '" & Me.Parent!PONumber & "'"

Linq ;0)>

Brilliant! works perfect, thanks so much - its easy when you know how hey!