Speed up excel formatting vba code?

Question

I am using the following vba code to change a text string date into an actual date in excel so I can use it for logical comparisons and the like.

The problem is I need t

Answer 1

It would be better to get the values in to an array in one single "pull", operate on the array and write it back. That would circumvent the expensive range operation.

dim c as range
set c = Range("D2:D" & Range("D" & Rows.Count).End(xlUp).Row)

dim ArrValue() as Variant

set ArrValue = c.value

next step: iterate over that array and then write back:

c.value = Arrvalue

I have no time to test the code, so please correct it for yourself, I am sorry.

Answer 2

First steps would be:

• Turn screen updating off
• Turn calculation off
• Read and write the range at once

It could look like the code below - it is a good idea to include an error handler to avoid leaving your spreadsheet with screen updates off or with the calculation mode changed:

Sub Datechange()

    On Error GoTo error_handler

    Dim initialMode As Long

    initialMode = Application.Calculation 'save calculation mode
    Application.Calculation = xlCalculationManual 'turn calculation to manual
    Application.ScreenUpdating = False 'turn off screen updating

    Dim data As Variant
    Dim i As Long

    'copy range to an array
    data = Range("D2:D" & Range("D" & Rows.Count).End(xlUp).Row)

    For i = LBound(data, 1) To UBound(data, 1)
        'modify the array if the value looks like a date, else skip it
        If IsDate(data(i, 1)) Then data(i, 1) = CDate(data(i, 1))
    Next i

    'copy array back to range
    Range("D2:D" & Range("D" & Rows.Count).End(xlUp).Row) = data

exit_door:
    Application.ScreenUpdating = True 'turn screen updating on
    Application.Calculation = initialMode 'restore original calculation mode

    Exit Sub

error_handler:
    'if there is an error, let the user know
    MsgBox "Error encountered on line " & i + 1 & ": " & Err.Description
    Resume exit_door 'don't forget the exit door to restore the calculation mode
End Sub