MiKTeX and proTeXt ⇒ Problem with index with MikTeX

[Forrest]

Hello,
I'm a newbie and I try to include an index with MikTeX and WinEdt using the following index.ist file :

headings_flag 1
heading_prefix "\n \\item \\textbf{"
heading_suffix "}"
symhead_positive "Symboles"
symhead_negative "symboles"
numhead_positive "Nombres"
numhead_negative "nombres"
delim_0 " \\dotfill\\ "
delim_1 " \\dotfill\\ "
delim_2 " \\dotfill\\ "

in order to change the usual index format.
The way I proceed is :
- I run Latex with \makeindex in my .tex file (called "myfile.tex"), in order to create "myfile.idx"
- I run "makeindex -s index.ist myfile.idx" in a command prompt in order to create the myfile.ind file
- I re-run Latex, but without the command \makeindex that would replace my former "myfile.ind" file (containing the format I want)

Unfortunately, Latex (MikTeX) replaces anyway the file "myfile.ind", even without the command "\makeindex" in "myfile.tex". So the final compilation happens each time with the wrong .ind file.
Is this normal ?
Thank you in advance for your help.