How to detect changes in cell format? - vba

Question

I want to embed a procedure in an Excel sheet that will detect when a cell's format changes, e.g. from Text to Number.
But I can't figure out how to get the cell's format type. I tried using the Worksheet_Change event handler to check the data type, as follows:
Private Sub worksheet_change(ByVal Target As Range)
If Target.Address = "a1" Then
If VarType(Target) <> 5 Then
MsgBox "cell format has been changed"
End If
End If
End Sub
But with this code in place, if I change cell A1's data type from Number to Text, Worksheet_Change is not triggered; the event handler is only called if I change the contents of the cell.
Also, this procedure can detect if the contents are changed from a number to an alphabetical string, e.g. from "35.12" to "abcd", but not Number-type number to Text-type number; if I set cell B1 to text, then enter "40", then paste the contents of cell B1 into cell A1, vartype() still returns "5", so the alert is not triggered.
How can I detect that the format has changed, regardless of whether the content type has changed?

Answer 1

Great question!
If you are only looking to trigger an event on the NumberFormat change (you appear to be calling this incorrectly the data format, NumberFormat is the attribute you want), the following is a good example.
I'm intercepting all selection change events and checking if any NumberFormat changed.
Option Explicit
'keep track of the previous
Public m_numberFormatDictionary As New dictionary
Public m_previousRange As Range
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
'requires reference to Microsoft Scripting Runtime
Dim c As Variant
Dim wasChange As Boolean
Debug.Print "***********************"
'make sure you had a previous selection and it was initialized
If m_numberFormatDictionary.Count > 0 And Not m_previousRange Is Nothing Then
'Iterate through all your previous formattings and see if they are the same
For Each c In m_previousRange
Debug.Print "Found " & c.NumberFormat & " in " & c.Address
Debug.Print "Stored value is " & m_numberFormatDictionary(c.Address) & " in " & c.Address
'print out when they are different
If c.NumberFormat <> m_numberFormatDictionary(c.Address) Then
Debug.Print "~~~~~~ Different ~~~~~~"
wasChange = True
End If
Next c
End If
'clear previous values
m_numberFormatDictionary.RemoveAll
'Make sure you don't error out Excel by checking a million things
If Target.Cells.Count < 1000 Then
'Add each cell format back into the previous formatting
For Each c In Target
Debug.Print "Adding " & c.NumberFormat & " to " & c.Address
m_numberFormatDictionary.Add c.Address, c.NumberFormat
Next c
'reset the range to what you just selected
Set m_previousRange = Target
End If
'simple prompt now, not sure what your use case is
If wasChange Then
MsgBox "There was at least one change!"
End If
End Sub
I'm not exactly sure what you are looking for, you'll have to modify the print/msgbox statements appropriately. Depending on your use case you may have to modify this slightly but it works in all my test examples.

Answer 2

there does not appear to be an event that fires when a cells format type changes.
however, I got this info from another forum site.
To edit a cells format without the use of a macro the cells must be selected (via left click then an icon, or right click). so, using the worksheets SelectionChanged, whenever a cell is selected you grab the format and address of that cell as well as check the address and format of the previous cell VS what the format of the previous cell is now. thus, if the format of the previous cell is different now than it was when last captured, it has been changed.
You can use this in conjuction with the change event, to see if the format has been changed between now (after the cells contents have changed) and when the cell was selected.
here's the link to the other forum as I cant claim this as my own invention:
http://www.mrexcel.com/forum/excel-questions/3704-calculate-format-change.html

Answer 3

Based on this response on StackOverflow here is some code that might work for you, assuming the change will be user generated and the selected range will change after they make the change...
Private Sub Worksheet_SelectionChange(ByVal Target As Range)
Static LastRange As Range
Static LastNumberFormat As String
If Not LastRange Is Nothing Then
If LastRange.Cells(1).NumberFormat <> LastNumberFormat Then
'Your action or message box notification goes here
End If
End If
Set LastRange = Target
LastNumberFormat = Target.NumberFormat
End Sub