No, it shouldn't be "in a way that". The expression "such that" has a precise mathematical meaning and nothing else will do here.

"Such That
A condition used in the definition of a mathematical object, commonly denoted : or |. For example, the rationals Q can be defined by
Q={p/q:q!=0,p,q in Z},
read as "the set of all p/q such that q!=0 and p,q in Z."
http://mathworld.wolfram.com/SuchThat.html

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Note added at 14 mins (2012-10-26 23:02:57 GMT)
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This page is well worth consulting:

"Don't use "so that" when you mean "such that"
Here are the definitions.

so that
1. In order that, as in I stopped so that you could catch up.
2. With the result or consequence that, as in Mail the package now so that it will arrive on time.
3. so ... that. In such a way or to such an extent that, as in The line was so long that I could scarcely find the end of it.
From dictionary.com

such that
1. adj : of a degree or quality specified (by the "that" clause); their anxiety was such that they could not sleep. (dictionary.com)
2. A condition used in the definition of a mathematical object. For example, the rationals can be defined as the set of all m/n such that n is nonzero and m and n are integers. (mathworld.wolfram.com)"
http://www.jmilne.org/math/words.html

It goes on to give examples and further explanation.

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Note added at 16 mins (2012-10-26 23:05:34 GMT)
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You may find this interesting; it's from the same page just cited:

"Probably the error arose from the influence of German on American (mathematical) English, since the two are not distinguished in German.
[From Matthias Künzer: They are distinguished:
Sei x in Q, so daß es ein m in Z\{0} mit xm in Z gibt.
Sei y in Q so, daß 3y in Z liegt.
Not very many German writers care. "After all, it's just a comma."]"


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Note added at 9 hrs (2012-10-27 08:42:58 GMT)
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"Such that" in mathematics (and in contexts analogous to its mathematical use) really expresses a condition; it means that the condition that follows "such that" or its mathematical notation (: or |) has to be fulfilled.

So your example refers to calculating the level _N in cases where the condition following "such that" is fulfilled: the equilibrium probability of being in a state in or above the level N_ is approximately zero.

"The set of (x,y) such that y is greater than 0 and less than f(x)" restricts the set of (x,y) to cases in which the condition after "such that" is fulfilled.