% This file is embedded in datatool-user.pdf version 3.0.1 2025-03-05
% Example 79 Adjusting the Item Hook to Calculate Totals and Show Negative Numbers in Red
% Label: "ex:balancesheet"
% arara: pdflatex
% arara: pdfcrop
\documentclass[12pt]{article}
\pagestyle{empty}
\begin{filecontents}[noheader,overwrite]{balance.csv}
Description,In,Out,Balance
Travel expenses,,230,-230
Conference fees,,400,-630
Grant,700,,70
Train fare,,70,0
\end{filecontents}
\usepackage{booktabs}
\usepackage{color}
\usepackage{datatool} 

\DTLsetup{store-datum,default-name=balance} 

\DTLread[
 headers={
  Description,
  in (\pounds),
  Out (\pounds),
  Balance (\pounds)
 }
]{balance.csv} 

\newcommand{\theInTotal}{0}
\newcommand{\theOutTotal}{0}
\RenewDocumentCommand \DTLdisplaydbAddItem { m m m m m m m m }
{% 
 \DTLifnullorempty{#2}{}% skip null or empty
 {% 
 \dtlifnumeq{#8}{4}% balance column
 {% 
  \DTLifnumlt{#2}{0}{\appto#1{\color{red}}}{}% 
 }% 
 {% 
  \dtlifnumeq{#8}{2}% in column
  {\DTLadd{\theInTotal}{\theInTotal}{#2}}% 
 {% 
  \dtlifnumeq{#8}{3}{\DTLadd{\theOutTotal}{\theOutTotal}{#2}}{}% out column
 }% 
 }% 
 \appto#1{#3{#2}}% 
 }% 
 } 
\begin{document}
\DTLaction[
 options={
  after-head={\midrule},
  foot={\midrule Totals & \theInTotal & \theOutTotal &}
 }
]{display} 
\end{document}