Capture [a-zA-Z] except for specific sequence of characters ("PT")

I have this capturing subgroup in my regex statement. What I am trying to achieve is to add an exception to the bold/first matching group ([a-zA-Z]{2}) which should not match the specific word "PT". I am using VBScript.RegEx which is said to be similar to Javascript RegEx.

([a-zA-Z]{2}|[a-zA-Z]{1}\d{1}|\d{1}[a-zA-Z]{1})

Refer to the table below for the decision tree.

>Solution :

You can use a negative lookahead conditional:

(?![Pp][Tt])\w{2}

The (?! means the next two characters should not match the value inside the parenthesis, in this case [Pp][Tt].

Try it on Regex101