Sorry, I don't really understand what you are trying to do, or better said, what the requirement is and which logic should be applied.
Using subfield() may be a reasonable way to do what you want, but without knowing what you need, it's hard to say.
Why don't you just post your current script and explain a bit more what you need to do in a more abstract way (how do you determine the noise values, for example? What are fields A, B for? do you need to concatenate the C values again after removing the noise?).
So maybe someone can suggest a more 'elegant' way or at least some alternative implementation.
Sorry Stefan if I was unclear.
I will still use subfield at a later step.
I needed to reduce information noise, meaning the values a and n that do not belong to the values between b and m.
I didn't want to post the entire code because I would have to place lots of code and people might not have the patience to read several lines of script. Hence the simplification.
What I am trying to do is create a bracket to perform interval matching.
Thanks for both of you