I have managed to get MimeTex working with WordPress now!
But nowI want to create a plugin that will replace everything between he tags
[tex] x^2 +y^2 [/tex]
<IMG SCR="http://mydomain.com/cgi-bin/mimetex.cgi? x^2+y^2 alt="x^2+y^2" border=0 align=middle>
But I don't really understand the plugin system...
Can anyone help?