Gnuplottex: Pass latex command to gnuplot script

I want to access and plot the same data from different LaTeX documents (a paper and a beamer presentation) using gnuplottex. The data and the gnuplot script is stored at some individual position relative to the two documents. To re-use as much code as possible, I would like to define the relative path to the data in each document in a macro, here datapath.

My question is: How can I pass the value of this command to the gnuplot script? I would basically like to use the following in my MWE:

plot datapath'/data.csv' using 1:2 with lines

I did find this thread. However I was unable to modify it to my needs. Can someone help me, please?

---

MWE

documentclass{article}

usepackage[latin1]{inputenx}
usepackage{filecontents}
usepackage[
  miktex,    % 
  subfolder, % generated graphs in a ”gnuplottex” subfolder
  cleanup,   % Delete the .gnuplot files after conversion
]{gnuplottex}

newcommand{datapath}{./ZZZ}

begin{document}

% This is the data file to be plotted from
begin{filecontents*}{datapath/data.csv}
Col1,Col2
0,0
1,1
end{filecontents*}

% This is the gnuplot script I would like to use the value of datapath in
begin{filecontents*}{datapath/script.gnuplot}
set key autotitle columnhead
set datafile separator "," # for csv-file
plot './ZZZ/data.csv' using 1:2 with lines
end{filecontents*}

begin{figure}[htbp]
centering
gnuplotloadfile[terminal=cairolatex]{datapath/script.gnuplot}
end{figure}

end{document}

newwritetempfile

immediateopenouttempfile=datapath/script.gnuplot
immediatewritetempfile{set key autotitle columnhead; 
set datafile separator ","; 
plot 'datapath/data.csv' using 1:2 with lines}
immediatecloseouttempfile