Excel VBA AutoFit runs slowly - vba

Question

I have an excel vba macro that creates and formats a sales quote. I have a function that autofits merged cells. I use this function to autofit description fields as some of them are long and some are short. On a typical quote, this function is called around 40 times. The macro completes in under a second. If I run the exact same macro again (perhaps with different settings on how it will display) it takes upwards of 30-60 seconds. There's nothing in the rest of the macro that slows down with each run except for the following block:
Is there something that could be making this code run slower for the exact same set of inputs?
Sub AutoFit_Height(ByVal Target As Range)
Dim MergeWidth As Single
Dim cM As Range
Dim CWidth As Double
Dim NewRowHt As Double
With Target
.MergeCells = False
CWidth = .Cells(1).ColumnWidth
MergeWidth = 0
For Each cM In Target
cM.WrapText = True
MergeWidth = cM.ColumnWidth + MergeWidth
Next
'small adjustment to temporary width
MergeWidth = MergeWidth + Target.Cells.count * 0.66
.Cells(1).ColumnWidth = MergeWidth
.EntireRow.AutoFit
NewRowHt = .RowHeight
.Cells(1).ColumnWidth = CWidth
.MergeCells = True
.RowHeight = NewRowHt
End With
End Sub

Answer 1

Go to the start of the main body of code (the one that calls this subroutine) and add
Application.ScreenUpdating = False
as one of the first lines. Then at the end of that function, after this subroutine has been called, turn it back on:
Application.ScreenUpdating = True
This will keep it from redrawing the screen for every change in column/row size, resulting in a significantly faster run time.

Answer 2

Optimazing your script might start with
using xlsb file saving extension
look for any unecessary formatting by deleting unused rows and
columns and saving so to make the vertical and horizontal scroll bar
scroll just to the necessary data
Use named range as much as possible
This could be added to your script
At the start of the main module from where you call other modules or functions
With Application
.DisplayAlerts = False
.ScreenUpdating = False
.Calculation = xlCalculationManual
.EnableEvents = False
End With
At the end of the main module task is complete
With Application
.DisplayAlerts = True
.ScreenUpdating = True
.Calculation = xlCalculationAutomatic
.EnableEvents = True
End With
As you are manipulating many worksheet objects that's quite a cpu intensive process. A change in algorithm could improve time needed for this process. Maybe you should post the entire code so to help you further.
Cheers,
Pascal
http://multiskillz.tekcities.com

Answer 3

Autofit is painfully slow for me to. The only thing I can add to any other answer here is to put it in a separate module and only call it when necessary or time is available. Also, to implement last, once all other code is tested and working.