使用正则表达式确定逗号分隔值是否有效

I have a string with comma separated alphanumeric values. The values are considered valid if they are exactly 2 characters in length, and if they have at least 1 alphabetical character. If all the values are valid then I would like to "capture" the entire string including commas. If a value is missing (back to back commas) then the entire string is invalid. I can only use Regex for this. Whitespace is ignored, the programming language used is JavaI have a string with comma separated alphanumer