Lookbehind on regex for VBA?

rich tier picture rich tier · Feb 5, 2012 · Viewed 10.1k times · Source

Is there a way to do negative and positive lookbehind in VBA regex?

I want to not match if the string starts with "A", so I am currently doing ^A at the start of the pattern, then removing the first character of match(0). Obviously not the best method!

I am using the regExp object.

Answer

brettdj picture brettdj · Feb 6, 2012

VBA offers positive and negative lookaheads but rather inconsistently not lookbehind.

The best example of using Regex with VBA that I have seen is this article by Patrick Matthews

[Updated example using Execute rather than Replace]

While I am not completely clear on your usage you could use a function like this with

  • skips any words starting with A
  • for all words not starting with a it returns everything from the second character on (using a submatch - the pattern inside ( and ) is submatch 1 -

    Sub TestString()
    MsgBox ReducedText("cfat dcat")
    MsgBox ReducedText("Sat all over the hat again")
    End Sub
    
    
    Function ReducedText(strIn As String) As String
    Dim objRegex As Object
    Dim objRegMC As Object
    Dim objRegM As Object
    Dim strOut As String
    Set objRegex = CreateObject("vbscript.regexp")
    With objRegex
      .IgnoreCase = True
      'not needed if matching the whole string
      .Global = True
      .Pattern = "\b[^a\s]([a-z]+)"
      If .test(strIn) Then
          Set objRegMC = .Execute(strIn)
          For Each objRegM In objRegMC
            strOut = strOut & objRegM.submatches(0) & vbNewLine
          Next
          ReducedText = strOut
      Else
        ReducedText = "Starts with A"
      End If
    End With
    End Function