VBA - Moving large number of records - some records missing - vba

Question

I have a data set of around 1500 sales records. I have written a macro, which would create product category specific work books, which would have an individual work sheet for each product in the product category.
The macro is working as expected, but I have found out that it is consistently ignoring some products. I put debug statements to see if I am getting zero records when I filter based on the product code (since I use this selection to paste the records to a separate work sheet). The selection seems to be working fine, as I get the number of rows selected.
A pattern I saw was that the product codes which were having zero records were generally the first ones or the last ones to get processed before or after a file operation (either I open a category specific work book, or I am closing a work book). But even here, the table header was copied to the individual work sheet. Only the data rows were getting ignored.
Is there a chance where the macro is processing the records too fast, while there is some time lag in doing File I/O operations (which makes a few records to get ignored)?
I am attaching the code, which I have used for looping
'loop through each row and get the product id and the category (Ann & Bnn).
' Dim catWorkBook As Workbook
oProductCat = "0" 'the initial value set as 0, which would NEVER be a category
With wkScrap 'this is a rough sheet which has the product items and categories
For i = 2 To lProdRow
cProductCode = .Cells(i, 1).Value
cProductCat = .Cells(i, 2).Value
'FILE OPEN: will need to open a category specific .xls file
If (StrComp(cProductCat, oProductCat) <> 0) Then
'save the existing workbook
FileIO.CloseExcelFile oProductCat, catWorkBook
Set catWorkBook = Nothing 'clear all traces of the old worksheet
Set catWorkBook = CreateBlankWorkBook()
oProductCat = cProductCat
End If
'COPY DATA: Filtering on product code, and then moving it into a new
'worksheet
CopyCategoryToWorksheet cProductCode, catWorkBook
If i = lProdRow Then
'we are at the end of the loop. Proceed to close the current
'workbook
FileIO.CloseExcelFile oProductCat, catWorkBook
End If
Next
End With
Here is the function which does the actual copying
Private Sub CopyCategoryToWorksheet(prodCode As String, catWkBook As Workbook)
'check for a meaningful prod code
If (Trim(prodCode & vbNullString) = vbNullString) Then
Exit Sub
End If
Dim wkRData As Worksheet
Dim rRData As Range
Dim rDataMaxRows As Integer
Set wkRData = SalesReport.Sheet1
'We know that we have to create a work sheet for this product code.
'Let us do that first.
Dim prodCatSheet As Worksheet
catWkBook.Activate
Set prodCatSheet = catWkBook.Sheets.Add(After:=catWkBook.Sheets(catWkBook.Sheets.Count))
prodCatSheet.Name = prodCode
wkRData.Activate 'for this sub routine, all processing is happening on the raw data sheet
rDataMaxRows = Cells(rows.Count, 1).End(xlUp).Row
Set rRData = Range("A1:H" & rDataMaxRows)
rRData.AutoFilter 3, Criteria1:="=" & Trim(prodCode)
rRData.Select
Selection.SpecialCells(xlCellTypeVisible).Select
Selection.Copy
'activate the newly created sheet, and paste all the selected rows there
prodCatSheet.Activate
prodCatSheet.PasteSpecial
Set wkRData = Nothing 'just clear some memory
End Sub