I need this asap.

I have a working wordpress blog.

I want to pass variables into posts
Example
http://blog.com?variable=passvariable.

I want to grab the variable from the url.

I have tried Jacks Static script plugin and can't make it work.
I have tried php print commands and phpexec plugin but my wordpress posts just end up replacing the php characters.

I need something that just allows me to add tags like this into the posts to grab the variable:

Example: I want the {{variable}} to appear in this post using this method.

I want this asap.