Appending data to a table only where it won't create a duplicate

Hi there,
I am copyng data from one table A to another B when a change has been made to the data in A. A is accessed via a form.
The change is made via an append query. Criteria limits the data in A but you cannot set criteria to append to table B if a field in B is different to that in A but not if it is the same.

I have attempted so far to create a new table with the data I want (this is meant to be temporary) in VBA.
The next step is to compare these values to those in Table B and where they are different append. Where they are the same to do nothing. I have used the following code but have made changes where appropriate to make the names fit my database. Consider shoes as B and import as the table created from the SQL code.

Public Function UpdateTableSeekNoStatus() As String
Dim dbs As Database, rstShoes As Recordset, rstImport As Recordset
Dim NumRec As Long

' Return reference to current database.
Set dbs = CurrentDb

' Create a dynaset-type Recordset object based on ShoeImport table.
Set rstImport = dbs.OpenRecordset("ShoeImport", dbOpenDynaset)

' Create a table-type Recordset object based on Shoes table.
Set rstShoes = dbs.OpenRecordset("Shoe")
' Set index for SEEK
rstShoes.Index = "PrimaryKey"

rstImport.MoveFirst

Do Until rstImport.EOF = True

rstShoes.Seek "=", rstImport!StockNumber, rstImport!Width

If rstShoes.NoMatch Then
If rstImport!TRNCOD = "U" Then
'Add a new Record
rstShoes.AddNew

rstShoes!StockNumber = rstImport!StockNumber
rstShoes!ShoeName = rstImport!ShoeName
rstShoes!Color = rstImport!Color
rstShoes!Width = rstImport!Width
rstShoes!VendorNumber = rstImport!VendorNumber
rstShoes!SKUNumber = rstImport!SKUNumber
rstShoes!Gender = rstImport!Gender
rstShoes!Brand = rstImport!Brand
rstShoes!TRNCOD = rstImport!TRNCOD
rstShoes!CurrentDate = rstImport!CurrentDate
rstShoes!CurrentTime = rstImport!CurrentTime

rstShoes.Update

End If

Loop

Where the problem exists for me, I think, is that 'Seek' requires an index to be used as a key. In my circumstances there is no key that relates between both tables, in fact there is no index in the created table. Is there another way of achieving what I am after, am I being overly elaborate with this.
Cheers
Tim