I have a regular string as bellow:

`xxSTART Here we have the first text in 1234 asdf xxENDxxSTART Here we have the second text 999 fffd xxENDxxSTART Here we have the third text 1234 9985Df xxENDxxSTART Here we have the fourth text 1234 asdf Dert xxEND`

I'm using the follow REGEX: `^(?:(.*?)\K(xxSTART)){3}(.*?xxEND)` to get ONLY third match `xxSTART Here we have the third text 1234 9985Df xxEND`. This work well in <http://www.regexr.com/v1/>, but i read a article saying `\K` option is not a option in C# ([Support of \K in regex](https://stackoverflow.com/questions/13542950/support-of-k-in-regex)), and the article [Translate Perl regular expressions to .NET](https://stackoverflow.com/questions/3417644/translate-perl-regex-to-net) say to use look-behind `((?<=…))` instead. But i cant use look-behind `((?<=…))` in my RegEX, anybody can help me? please!!

Anyone have a ideia how to use `((?<=…))` in my RegEX `^(?:(.*?)\K(xxSTART)){3}(.*?xxEND)` to replace `\K` option?

Thank Regards,