XeLaTeX, Landscape Setting Papersize for PSTricks Graphic

Question

I found that my PSTricks Graphics only work in Landscape when I edit the dvipdfmx.cfg and add -sPAPERSIZE=a0 to the line

%% Use MiKTeX Ghostscript:
D  "mgs.exe -q -dNOPAUSE -dBATCH -dEPSCrop -sPAPERSIZE=a0 -sDEVICE=pdfwrite -dCompatibilityLevel=%v -dAutoFilterGrayImages=false -dGrayImageFilter=/FlateEncode -dAutoFilterColorImages=false -dColorImageFilter=/FlateEncode -sOutputFile=\"%o\" \"%i\" -c quit"

But at my WorkPC I don't have access to this .cfg file

Can I achieve the same, from out of TexWorks (I use Miktex 2.9) or out of the document somehow? I want a PDF Output.

I can't use other LaTeX editors, or other MikTeX versions.

Example:

\documentclass[a4paper,9pt]{extarticle}
\usepackage{helvet}
\usepackage[utf8]{inputenc}
\usepackage{scrextend}
\usepackage[newdimens]{labels}
\usepackage{pstricks}
\usepackage{pst-barcode}
\usepackage{geometry}

\geometry{
landscape, 
margin=0mm
}

\newcommand{\sap}[2]{
\centering\begin{pspicture}(0,0)(7,4)\psbarcode[scaley=1.5]{#2}{includetext textsize=10 width=2.8}{code128}
\end{pspicture}}

\begin{document}

\LabelCols=2
\LabelRows=2
\LabelSetup
\begin{labels}
\sap{Gblalbla1}{209ss4}
\sap{GGblalbla1}{20ss9214}
\sap{Gblalbla}{2092ss141}
\sap{blablabal}{209ss214}%
\end{labels}

\end{document}

Answer 1

No problem with up-to-date TL2015:

\documentclass[landscape,a4paper,10pt]{article}
\usepackage{helvet}
\usepackage[margin=0pt]{geometry}
\usepackage[newdimens]{labels}
\LabelCols=2
\LabelRows=2
\LabelSetup
\usepackage{pst-barcode}

\newcommand{\sap}[2]{\centering
\begin{pspicture}(0,-0.2in)(2.8in,1.5in)\psbarcode[scaley=1.5]{#2}{includetext
 textsize=10 width=2.8}{code128}
\end{pspicture}}

\begin{document}

\begin{labels}
\sap{Gblalbla1}{209ss4}

\sap{GGblalbla1}{20ss9214}

\sap{Gblalbla}{2092ss141}

\sap{blablabal}{209ss214}

\end{labels}

\end{document}

Answer 2

I found it myself.

You have to go to the CMD Shell and type

initexmf --edit-config-file dvipdfmx

this will create a config File in your Windows User Directory, which even in Workplaces usually is not write protected. In this file you can make any changes, and the original file will be overwritten.