[Therion] >> data.mp

[Markus Boldt]

Hi, 
I have a question related the possibility to
change font sizes as given in Therion wiki with a
metapost-code. 
What have I done? 
In config-file I have written: 
code metapost
   def fonts_setup (expr t,s,m,l,h) =
write "\def\thstationname{\size[4]}" to
"mptexpre.tex"; 
write EOF to "mptexpre.tex";
   enddef;
   initialize(Scale);
   endcode

But I get this error: 
>> data.mp
>> data.mpx
! Unable to make mpx file.
l.6931 p_label(btex
                    \thlabel\thnormalsize
\vbox{\halign{\hfil#\hfil\cr\thfb\...
The two files given above are one of your source
files
and an auxiliary file I need to read to find out
what your
btex..etex blocks mean. If you don't know why I
had trouble,
try running it manually through MPtoTeX, TeX, and
DVItoMP

Then I have searched for that file called
"mptexpre.tex" But I havn`t found it. What is
wrong? 

Greetings and best eastern for you all! 
Markus 

PS. I use the Windows Installation 5.3.16 on
win2010