I have currently the Latex code written in the .cls file to display a list of abbreviations as follows:
\newcommand\listnomenclature{Abbreviations}
\usepackage{longtable}
\newcommand\listofnomenclature[2]{
\btypeout{\listnomenclature}
\addtotoc{\listnomenclature}
\chapter*{\listnomenclature
\@mkboth{
\MakeUppercase\listnomenclature}{\MakeUppercase\listnomenclature}}
\begin{longtable}[c]{#1}#2\end{longtable}\par
\cleardoublepage
}
It is used in the following way:
\listofnomenclature{ll}{
GHG & GreenHouse Gasses \\
CoMP & Cooperative Multi-Point \\
ITU & International Telecommunication Union \\
}
Is it possible to modify the codes in the .cls file so that the output is sorted alphanumerically without drastically changing the way it is used?

glossariespackage? It has many bells and whistles, among which treatment of acronyms and lists thereof. – egreg Dec 10 '12 at 10:16