Extract specific substring which not preceding with specified substring

Question

I have a question that is relatively simple but brought me to the wall. I want to have a regex do following task in VBA (VBScript_RegExp_5.5).

Given a string like this:

"PrivateFactoryAsclsFactoryPrivateFactoryAsclsFactory"

I want to remove only the occurrences of "Factory" that are not preceded by "cls". For this particular case, if all matches are correctly replaced with "_", the result will look like this:

"Private_AsclsFactoryPrivate_AsclsFactory"

Of course, a simple exclusion trick like "clsFactory|(Factory)" does not works in VBA, nor do look-behinds.

Answer 1

You actually can do a negative lookbehind with a bit of a hack using the VBScript Regex library. The following pattern matches any two or less characters or any three characters that aren't "cls" (using a negative lookahead), followed by "Factory".

Const strText As String = "PrivateFactoryAsclsFactoryPrivateFactoryAsclsFactory"

With CreateObject("VBScript.RegExp")
    .Pattern = "(^.{0,2}|(?!cls).{3})Factory"
    .Global = True
    Debug.Print .Replace(strText, "$1_")
End With

Output:

Private_AsclsFactoryPrivate_AsclsFactory