How to improve slow macro?

Question

I need to use Word Macro for automatically proofreading the documents. I have an excel file, filled in with all the wrong spelling words, and after I installed the macro to Microsoft Word, it took several minutes to finish the spelling checking for just 1 page of the Word Document.

Can I use .txt to replace the excel in order to make it faster? Or what should I improve? Below please find the code for the Macro:

Attribute VB_Name = "PR"

Option Explicit 

Sub PR() 
    Dim Path As String
    Dim objExcel As Object 
    Dim iCount As Integer 
    Dim VChar As String 
    Dim OChar As String  

    Options.AutoFormatAsYouTypeReplaceQuotes = True     

    Path = "D:\Macro\rplPR.xlsx" 

    'Highlight variant characters 
    With ActiveDocument 
        .TrackRevisions = False 
        .ShowRevisions = False 
    End With       

    Set objExcel = CreateObject("Excel.Application") 
    objExcel.Workbooks.Open Path      

    For iCount = 2 To 2500 

        Selection.HomeKey Unit:=wdStory 
        VChar = objExcel.ActiveWorkbook.Sheets(1).Cells(iCount, 1)                                 

        If Len(VChar) = 0 Then Exit For           

        Selection.HomeKey Unit:=wdStory, Extend:=wdMove          

        With Selection.Find 
            .ClearFormatting 
            .Replacement.ClearFormatting 
            .Replacement.Highlight = True 
            .Text = VChar 
            .Replacement.Text = "^&" 
            .Execute Replace:=wdReplaceAll 
        End With             
    Next             

    objExcel.ActiveWorkbook.Close 
    objExcel.Quit      

End Sub 

Answer 1

Try the following. Do note that there is necessarily some overhead involved in starting Excel (if not already running), as well as processing the workbook. Hence, even a single-page document will encounter the same overhead there as a 100-page document.

Sub BulkFindReplace()
Application.ScreenUpdating = False
Dim xlApp As Object, xlWkBk As Object, StrWkBkNm As String, StrWkSht As String
Dim iDataRow As Long, xlFList As String, xlRList As String, i As Long
StrWkBkNm = "D:\Macro\rplPR.xlsx": StrWkSht = "Sheet1"
'Start Excel
Set xlApp = CreateObject("Excel.Application")
If xlApp Is Nothing Then
  MsgBox "Can't start Excel.", vbExclamation
  Exit Sub
End If
On Error GoTo 0
With xlApp
  'Hide our Excel session
  .Visible = False
  ' The file is available, so open it.
  Set xlWkBk = .Workbooks.Open(StrWkBkNm, False, True)
  If xlWkBk Is Nothing Then
    MsgBox "Cannot open:" & vbCr & StrWkBkNm, vbExclamation
    .Quit: Set xlApp = Nothing: Exit Sub
  End If
  ' Process the workbook.
  With xlWkBk
    With .Worksheets(StrWkSht)
      ' Find the last-used row in column A.
      iDataRow = .Cells(.Rows.Count, 1).End(-4162).Row ' -4162 = xlUp
      ' Capture the F/R data.
      For i = 1 To iDataRow
        ' Skip over empty fields to preserve the underlying cell contents.
        If Trim(.Range("A" & i)) <> vbNullString Then
          xlFList = xlFList & "|" & Trim(.Range("A" & i))
          xlRList = xlRList & "|" & Trim(.Range("B" & i))
        End If
      Next
    End With
  .Close False
  End With
  .Quit
End With
' Release Excel object memory
Set xlWkBk = Nothing: Set xlApp = Nothing
'Exit if there are no data
If xlFList = "" Then Exit Sub
'Process each word from the F/R List
With ActiveDocument.Range.Find
  .ClearFormatting
  .Replacement.ClearFormatting
  .MatchWholeWord = True
  .MatchCase = False
  .Wrap = wdFindContinue
  For i = 1 To UBound(Split(xlFList, "|"))
    .Text = Split(xlFList, "|")(i)
    .Replacement.Text = Split(xlRList, "|")(i)
    .Execute Replace:=wdReplaceAll
  Next
End With
Application.ScreenUpdating = True
End Sub

Answer 2

Move these lines up to above the For statement. You are setting them 2,499 times and you only need to do it once.

        .ClearFormatting 
        .Replacement.ClearFormatting 
        .Replacement.Highlight = True 
        .Text = VChar 
        .Replacement.Text = "^&" 

So each dot is a function call. There are 5 needless ones done 2498 times which is 12,490 function calls.

Function calls, while essential, are slow compared to other operations as there is a lot of setup.

If you didn't use with that would be an extra 12,490 function calls as well for a total of 24,980 sloww needless function calls.