custom bbcode

[sde]

i want to add a new bbcode which requires server-side processing. is thi possible?

for example, some_string > <.

then i'd like to take the text inside the new bbcode brackets and process it server side. i've been able to get the contents of it, but the > and < are already translated to &gt; and &lt;

i need the raw text to process.

any ideas, links, or suggestions?