Excel cell content validation with use of VBA code - vba

Question

I am looking for a solution to validate and highlight my cell in case false.
I tried the most promising solution: Regex. But still can not find the pattern I need.
My latest attempt was this pattern: "[A-Z-0-9_.]" This works only if the cell contains only a symbol and nothing else, if the symbol is part of a string it does not work.
Problem is that it does not catch cells that have an odd character in a string of text: Example C4UNIT| or B$GROUP.
Specification Cell can contain only capital characters and two allowed symbols Dash - and Underbar _
This is my complete code:
Function ValidateCellContent()
Sheets("MTO DATA").Select
Dim RangeToCheck As Range
Dim CellinRangeToCheck As Range
Dim CollNumberFirst As Integer
Dim CollNumberLast As Integer
Dim RowNumberFirst As Integer
Dim RowNumberLast As Integer
'--Start on Column "1" and Row "3"
CollNumberFirst = 1
RowNumberFirst = 3
'--Find last Column used on row "2" (Write OMI Headings)
CollNumberLast = Cells(2, Columns.count).End(xlToLeft).Column
RowNumberLast = Cells(Rows.count, 1).End(xlUp).Row
'--Set value of the used range of cell addresses like: "A3:K85"
Set RangeToCheck = Range(Chr(64 + CollNumberFirst) & RowNumberFirst & ":" & Chr(64 + CollNumberLast) & RowNumberLast)
Debug.Print "Cells used in active Range = " & (Chr(64 + CollNumberFirst) & RowNumberFirst & ":" & Chr(64 + CollNumberLast) & RowNumberLast)
For Each CellinRangeToCheck In RangeToCheck
Debug.Print "CellinRangeToCheck value = " & CellinRangeToCheck
If Len(CellinRangeToCheck.Text) > 0 Then
'--Non Printables (Space,Line Feed,Carriage Return)
If InStr(CellinRangeToCheck, " ") _
Or InStr(CellinRangeToCheck, Chr(10)) > 0 _
Or InStr(CellinRangeToCheck, Chr(13)) > 0 Then
CellinRangeToCheck.Font.Color = vbRed
CellinRangeToCheck.Font.Bold = True
'--Allowed Characters
ElseIf Not CellinRangeToCheck.Text Like "*[A-Z-0-9_.]*" Then
CellinRangeToCheck.Font.Color = vbRed
CellinRangeToCheck.Font.Bold = True
Else
CellinRangeToCheck.Font.Color = vbBlack
CellinRangeToCheck.Font.Bold = False
End If
End If
Next CellinRangeToCheck
End Function

Answer 1

Try this:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
'we want only validate when cell content changed, if whole range is involved (i.e. more than 1 cell) then exit sub
If Target.Cells.Count > 1 Then Exit Sub
'if there is error in a cell, also color it red
If IsError(Target) Then
Target.Interior.ColorIndex = 3
Exit Sub
End If
'validate cell with our function, if cell content is valid, it'll return True
'if it i s not valid, then color cell red
If Not ValidateText(Target.Value) Then
Target.Interior.ColorIndex = 3
End If
End Sub
Function ValidateText(ByVal txt As String) As Boolean
Dim i As Long, char As String
'loop through all characters in string
For i = 1 To Len(txt)
char = Mid(txt, i, 1)
If Not ((Asc(char) >= 65 And Asc(char) <= 90) Or char = "-" Or char = "_") Then
'once we come upon invalid character, we can finish the function with False result
ValidateText = False
Exit Function
End If
Next
ValidateText = True
End Function

Answer 2

I've originally assumed you wanted to use RegEx to solve your problem. As per your comment you instead seem to be using the Like operator.
Like operator
While Like accepts character ranges that may resemble regular expressions, there are many differences and few similarities between the two:
Like uses ! to negate a character range instead of the ^ used in RegEx.
Like does not allow/know quantifiers after the closing bracket ] and thus always matches a single character per pair of brackets []. To match multiple characters you need to add multiple copies of your character range brackets.
Like does not understand advanced concepts like capturing groups or lookahead / lookbehind
probably more differences...
The unavailability of quantifiers leaves Like in a really bad spot for your problem. You always need to have one character range to compare to for each character in your cell's text. As such the only way I can see to make use of the Like operator would be as follows:
Private Function IsTextValid(ByVal stringToValidate As String) As Boolean
Dim CharValidationPattern As String
CharValidationPattern = "[A-Z0-9._-]"
Dim StringValidationPattern As String
StringValidationPattern = RepeatString(CharValidationPattern, Len(stringToValidate))
IsTextValid = stringToValidate Like StringValidationPattern
End Function
Private Function RepeatString(ByVal stringToRepeat As String, ByVal repetitions As Long) As String
Dim Result As String
Dim i As Long
For i = 1 To repetitions
Result = Result & stringToRepeat
Next i
RepeatString = Result
End Function
You can then pass the text you want to check to IsTextValid like that:
If IsTextValid("A.ASDZ-054_93") Then Debug.Print "Hurray, it's valid!"
As per your comment, a small Worksheet_Change event to place into the worksheet module of your respective worksheet. (You will also need to place the above two functions there. Alternatively you can make them public and place them in a standard module.):
Private Sub Worksheet_Change(ByVal Target As Range)
Dim ValidationRange As Range
Set ValidationRange = Me.Range("A2:D5")
Dim TargetCell As Range
For Each TargetCell In Target.Cells
' Only work on cells falling into the ValidationRange
If Not Intersect(TargetCell, ValidationRange) Is Nothing Then
If IsTextValid(TargetCell.Text) Then
TargetCell.Font.Color = vbBlack
TargetCell.Font.Bold = False
Else
TargetCell.Font.Color = vbRed
TargetCell.Font.Bold = True
End If
End If
Next TargetCell
End Sub
Regular Expressions
If you want to continue down the RegEx road, try this expression:
[^A-Z0-9_-]+
It will generate a match, whenever a passed-in string contains one or more characters you don't want. All cells with only valid characters should not return a match.
Explanation:
A-Z will match all capital letters,
0-9 will match all numbers,
_- will match underscore and dash symbols.
The preceding ^ will negate the whole character set, meaning the RegEx only matches characters not in the set.
The following + tells the RegEx engine to match one or more characters of the aforementioned set. You only want to match your input, if there is at least one illegal char in there. And if there are more than one, it should still match.
Once in place, adapting the system to changing requirements (different chars considered legal) is as easy as switching out a few characters between the [brackets].
See a live example online.