slow cell formatting using vba? - vba

Question

Disclaimer: I am relatively new to vba and macros.
I have written a macro to update value and formatting in some individual cells after reading and parsing a json through http and the process is very slow, so I broke down the code into different portions to see where the bottleneck might be. Turns out the cell updating is the problem, I have the following code:
Sub test()
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual
Application.EnableEvents = False
Application.EnableCancelKey = False
t = Timer
With Range("A1")
.Font.Italic = True
.Interior.ColorIndex = 37
.Value = 3412
End With
Debug.Print Timer - t
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
Application.EnableEvents = True
Application.EnableCancelKey = True
End Sub
the debug print is about 0.3 to 0.5 sec... I have afterwards further wrapped the timer around each of the italic, colorIndex, and value lines and they all turns out take about 0.015 sec each... I have tried searching online how to make the code more efficient, hence the screenupdating toggles as well as no selection, but 0.5 sec still seem a bit slow in updating a cell to me.
please note that I am not whining, I just want to know if I am doing the right thing here. Is there a more efficient way to implement the formatting and value changes that I posted here, or is it just a fact that excel takes this amount of time to update the cell? I am just very curious because the json reading and parsing that I also implemented are significantly faster than this.
Also I have tested this script on at least 3 computers and they all take around the same time so I don't think it's an individual computer problem. And I used excel 2007 and 2010 to test.

Answer 1

I assume you are wanting to format more than a single cell? If so, it will be faster to create a range reference to all the cells requiring the same format (it need not be contiguous), then apply the required format to that range object in one step
Following example demo's creating a range reference, and applying format in one go
Option Explicit
Private Declare Function GetTickCount Lib "kernel32" () As Long
Sub Demo()
Dim t As Long
Dim n As Long, i As Long
Dim m As Long
Dim ws As Worksheet
Dim cl As Range
Dim rSearch As Range
Dim rResult As Range
Set ws = ActiveSheet ' or another sheet...
Set rSearch = ws.Range("A1:A1000")
' note, this is an inefficient loop, can be made much faster
' details will depend on the use case
For Each cl In rSearch
' determine if cell is to be formatted
If cl.Row Mod 2 = 0 Then
' add cl to Result range
If rResult Is Nothing Then
Set rResult = cl
Else
Set rResult = Application.Union(rResult, cl)
End If
End If
Next
Debug.Print "Result Range includes ", rResult.Cells.Count, "Cells"
t = GetTickCount
' Apply format
With rResult
.Font.Italic = True
.Interior.ColorIndex = 37
.Value = 3412
End With
Debug.Print (GetTickCount - t) / 1000, "seconds"
End Sub