1) I've found the source of my solution where I had read it at first:
2) And I also found a link which can help to write a custom EL function
I'm gonna check it later and write about the results in my blog.
Please check this link also: http://www.ilikespam.com/blog/el-function-parameters-with-jboss-el
Also RichFaces CDK has built-in support for functions: http://anonsvn.jboss.org/repos/richfaces/tags/3.3.3.Final/ui/functions/src/main/config/component/functions.xml
Thanks Nick. Both links are very useful. I'm gonna check RichFaces CDK later for JSF 2.0. I guess I found an enough appropriate solution for JSF 1.2. But anyway thank you very much that you've connected to this discussion.