How to test for specific characters with regex in VBA - regex

Question

I need to test for a string variable to ensure it matches a specific format:
XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX
...where x can be any alphanumerical character (a - z, 0 - 9).
I've tried the following, but it doesn't seem to work (test values constantly fail)
If val Like "^([A-Za-z0-9_]{8})([-]{1})([A-Za-z0-9_]{4})([-]{1})([A-Za-z0-9_]{4})([-]{1})([A-Za-z0-9_]{4})([-]{1})([A-Za-z0-9_]{12})" Then
MsgBox "OK"
Else
MsgBox "FAIL"
End If
.
fnCheckSubscriptionID "fdda752d-32de-474e-959e-4b5bf7574436"
Any pointers? I don't mind if this can be achieved in vba or with a formula.

Answer 1

You are already using the ^ beginning-of-string anchor, which is terrific. You also need the $ end-of-string anchor, otherwise in the last group of digits, the regex engine is able to match the first 12 digits of a longer group of digits (e.g. 15 digits).
I rewrote your regex in a more compact way:
^[A-Z0-9]{8}-(?:[A-Z0-9]{4}-){3}[A-Z0-9]{12}$
Note these few tweaks:
[-]{1} can just be expressed with -
I removed the underscores as you say you only want letters and digits. If you do want underscores, instead of [A-Z0-9]{8} (for instance), you can just write \w{8} as \w matches letters, digits and underscores.
Removed the lowercase letters. If you do want to allow lowercase letters, we'll turn on case-insensitive mode in the code (see line 3 of the sample code below).
No need for (capturing groups), so removed the parentheses
We have three groups of four letters and a dash, so wrote (?:[A-Z0-9]{4}-) with a {3}
Sample code
Dim myRegExp, FoundMatch
Set myRegExp = New RegExp
myRegExp.IgnoreCase = True
myRegExp.Pattern = "^[A-Z0-9]{8}-(?:[A-Z0-9]{4}-){3}[A-Z0-9]{12}$"
FoundMatch = myRegExp.Test(SubjectString)

Answer 2

You can do this either with a regular expression, or with just native VBA. I am assuming from your code that the underscore character is also valid in the string.
To do this with native VBA, you need to build up the LIKE string since quantifiers are not included. Also using Option Compare Text makes the "like" action case insensitive.
Option Explicit
Option Compare Text
Function TestFormat(S As String) As Boolean
'Sections
Dim S1 As String, S2_4 As String, S5 As String
Dim sLike As String
With WorksheetFunction
S1 = .Rept("[A-Z0-9_]", 8)
S2_4 = .Rept("[A-Z0-9_]", 4)
S5 = .Rept("[A-Z0-9_]", 12)
sLike = S1 & .Rept("-" & S2_4, 3) & "-" & S5
End With
TestFormat = S Like sLike
End Function
With regular expressions, the pattern is simpler to build, but the execution time may be longer, and that may make a difference if you are processing very large amounts of data.
Function TestFormatRegex(S As String) As Boolean
Dim RE As Object
Set RE = CreateObject("vbscript.regexp")
With RE
.Global = True
.MultiLine = True
.Pattern = "^\w{8}(?:-\w{4}){3}-\w{12}$"
TestFormatRegex = .test(S)
End With
End Function

Answer 3

Sub Test()
MsgBox fnCheckSubscriptionID("XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX")
End Sub
Function fnCheckSubscriptionID(strCont)
' Tools - References - add "Microsoft VBScript Regular Expressions 5.5"
With New RegExp
.Pattern = "^\w{8}-\w{4}-\w{4}-\w{4}-\w{12}$"
.Global = True
.MultiLine = True
fnCheckSubscriptionID = .Test(strCont)
End With
End Function
In case of any problems with early binding you can use late binding With CreateObject("VBScript.RegExp") instead of With New RegExp.