Find invalid data validation cells - vba

Question

Description:
I have created a custom dropdown data validation list where I can choose among several values. These values on the dropdown list changes as I need (are defined in a worksheet column X).
Problem:
My problem occurs when I choose one of those values, let say Y, from the dropdown list and then I update the data validation by removing the last inserted value (deleted the Y value from column X). By doing this the value Y present in the worksheet is no longer valid so I would like to know if there is a way to obtain a list (array or string) of cells with the invalid data.
What I have done/thought so far:
I have searched in several sites and read similar questions but I cannot find anything usefull. I thought about looping all the cells and check if the value is valid but since I have a huge amount of data I think that it is not the best approach.
Since Excel already mark these invalid data with a red circle maybe it could be possible to get the address of those marked cells?
Thanks in advance!

Answer 1

The correct way to obtain the invalid cells in a worksheet is using Cells.SpecialCells(xlCellTypeAllValidation).
By using some information present in Microsoft KB213773 (Q213773) - "How to create data validation circles for printing in Excel" a similar Sub can be used to loop all invalid cells and then change their values (or mark them to future edit).
Sub CorrectInvalidValues()
Dim data_range As Range
Dim invalid_cell As Range
Dim count As Integer: count = 0
Dim nr_invalid As Integer: nr_invalid = 0
Dim new_value As String
'If an error occurs run the error handler and end the procedure
On Error GoTo errhandler
Set data_range = Cells.SpecialCells(xlCellTypeAllValidation)
On Error GoTo 0
' Loop through each cell that has data validation and gets the number of invalid cells
For Each invalid_cell In data_range
If Not invalid_cell.Validation.Value Then
nr_invalid = nr_invalid + 1
End If
Next
' Editing each value
For Each invalid_cell In data_range
If Not invalid_cell.Validation.Value Then
count = count + 1
Application.Goto reference:=invalid_cell, Scroll:=True
new_value = Application.InputBox("Please insert a correct value.", "Invalid Data " & count & "/" & nr_invalid)
If Not (new_value = "False") Then
invalid_cell.Interior.ColorIndex = 0
invalid_cell.Value = new_value
Else
invalid_cell.Interior.Color = RGB(255, 0, 0)
invalid_cell.Value = "<PLEASE EDIT>"
End If
End If
Next
Exit Sub
errhandler:
MsgBox "There are no cells with data validation on this sheet."
End Sub