control characters check taking too long to load - vba

Question

I am trying to search for special characters in a string.
If the special character exists in the string then the code would return a false to the adjacent cell.
Dim arr(5)
arr(1) = "19"
arr(2) = "26"
arr(3) = "29"
arr(4) = "32"
arr(5) = "50"
'control characters check
For n = 1 To 5
For x = 1 To 41
If InStr(1, Range("b" & arr(n)), Chr(x)) = 0 Then
For y = 123 To 255
If InStr(Range("b" & arr(n)).Value, Chr(y)) > 0 Then
Range("e" & arr(n)).Value = "FALSE"
Exit For
Else
Range("e" & arr(n)).Value = "TRUE"
End If
Next y
Else
Range("e" & arr(n)).Value = "FALSE"
Exit For
End If
Next x
Next n
My problem is, just looping a few times took quite a long time, is there a faster way to loop through all the data saving more time?
An example of the string data in the cell is : TY56D-CAT131BP342AC46-eL-W-00

Answer 1

Try this:
Sub Test()
Dim arr(5) As String
Dim iLen As Integer, strV As String
Dim Found As Boolean: Found = False
Dim Test As Variant
arr(1) = "19"
arr(2) = "26"
arr(3) = "29"
arr(4) = "32"
arr(5) = "50"
For x = 1 To 5
iLen = Len(Range("B" & arr(x)).Value)
strV = Range("B" & arr(x)).Value
For i = 1 To iLen
Select Case Asc(Mid$(strV, i, 1))
Case 1 To 41, 123 To 255
Found = True
Exit For
End Select
Next i
If Found = False Then
Range("E" & arr(x)).Value = "TRUE"
Else
Found = False
Range("E" & arr(x)).Value = "FALSE"
End If
Next x
End Sub
Calculation time is nearly instant. What differs to your method is, that i go through every characters and then check if its allowed or not. In this case the Select Case can do this much quicker than a for loop for every unallowed char.

Answer 2

It looks like you're being slowed down a lot by referring to
Range("b" & arr(n)).Value
potentially up to 120+ times in the loop (which is itself nested in other loops)
What should immediately improve the speed of your macro is to transfer the Range value to a variable before this loop, for example:
dim search_string as string
search_string = Range("b" & arr(n)).Value
For y = 123 To 255
If InStr(search_string, Chr(y)) > 0 Then
Range("e" & arr(n)).Value = "FALSE"
You'd also save a bit of time converting your whole search range to an array and working on that, but that would take more work, whereas this is a quick change you can make which should drastically improve performance

Answer 3

Try this:
Sub CheckCharacters()
Dim cl(5) As Integer, n As Integer
cls = Array(19, 26, 29, 32, 50)
For n = 0 To 4
If IsValidString(Range("B" & cls(n))) Then
Range("B" & cls(n)).Offset(0, 3) = "TRUE"
Else
Range("B" & cls(n)).Offset(0, 3) = "FALSE"
End if
Next n
End Sub
Function IsValidString(str As String) As Boolean
Dim objRegEx As Object
Set objRegEx = CreateObject("vbscript.regexp")
objRegEx.Pattern = "^[\x2a-\x7a]+"
objRegEx.Global = True
objRegEx.IgnoreCase = True
IsValidString = objRegEx.test(str)
End Function
The important bit is:
"^[\x2a-\x7a]+"
This is a Regex that is only TRUE if the string only contains characters between ASCII values 42 and 122 (which is what you want).