Wie entlese ich einer pgfplotstable Werte, die von mehreren Parametern abhängen?

\documentclass[varwidth, border=10pt]{standalone}
%\documentclass[paper=a5]{scrbook}
%\usepackage[left=1cm, right=1cm]{geometry}

\usepackage{pgfplotstable}
\usepackage{filecontents}

\begin{document}
\begin{filecontents}{n5.txt}
5   0   0.59049 0.32768 0.23730 0.16807 0.07776 0.03125
5   1   0.91854 0.73728 0.63281 0.52822 0.33696 0.18750
5   2   0.99144 0.94208 0.89648 0.83692 0.68256 0.50000
5   3   0.99954 0.99328 0.98438 0.96922 0.91296 0.81250
5   4   0.99999 0.99968 0.99902 0.99757 0.98976 0.96875
\end{filecontents}
\begin{filecontents}{n10.txt}
10 0 0.34868    0.10737 0.05631 0.02825 0.00605 0.00098
10 1 0.73610    0.37581 0.24403 0.14931 0.04636 0.01074
10 2 0.92981    0.67780 0.52559 0.38278 0.16729 0.05469
10 3 0.98720    0.87913 0.77588 0.64961 0.38228 0.17188
10 4 0.99837    0.96721 0.92187 0.84973 0.63310 0.37695
10 5 0.99985    0.99363 0.98027 0.95265 0.83376 0.62305
10 6 0.99999    0.99914 0.99649 0.98941 0.94524 0.82813
10 7 1.00000    0.99992 0.99958 0.99841 0.98771 0.94531
10 8 1.00000    1.00000 0.99997 0.99986 0.99832 0.98926
10 9 1.00000    1.00000 1.00000 0.99999 0.99990 0.99902
\end{filecontents}
% ....    HIER WEITERE
% Tabellen einlesen
\pgfplotstableread{n5.txt}{\nV} % "n Römische Zahl" geht das auch besser?
\pgfplotstableread{n10.txt}{\nX}    
% ....    HIER WEITERE
% --------------------------
% Tabellen ausgeben
\pgfplotstabletypeset{\nV} \\
%\pgfplotstabletypeset{\nX} \\
% ....    HIER WEITERE
% --------------------------

\def\getcell#1#2{
\pgfplotstablegetelem{#1}{#2}\of{\nV}\pgfplotsretval%
}

$P(X \leq k) = F(n,p;k) = \getcell{0}{2}$

$P(X = k) = P(X \leq k) - P(X \leq k-1) = F(n,p;k) - F(n,p;k-1)  = ???$

\end{document}