Capturing text between two words using a regular expression

I am trying to get the text in between two keywords using a regular expression in CSharp. Although I already found a topic with the same heading, that one was about finding the text in between square brackets, which is rather easy, since you can use `\[(?<blah>[^\]]+?)\]` to do this. What I am trying to do is finding the words `Matched text 123./!` in `UnMatched text 123./!team`. So my delimiters are `Un` and `team`. If I would build my RegEx the way I am used to, I would need to do three parts again: `Un` for the start delimiter at the beginning, `team` for the end delimiter at the end and a group `(?<blah>...+?)` which says "Anything but the string `team`". But I dunno how to express this in regular expressions. Is there a way to say "not this string" instead of "not one of those characters"? Also since I don't know about differences between implementations of Regular Expressions: I am using `System.Text.RegularExpressions.RegEx` of the .NET-Framework to parse them, so of course the sample should be working with this implementations.