[Boost-users] [preprocessor] removing parentheses

I have a single macro parameter which allows its passed value to contain commas. Therefore the user of the macro needs parentheses around the parameter if it contains one or more commas ( to does not have to ). When processing this parameter in a macro I would like to remove the outer parentheses if they are there before passing the value on for further processing. Is there a way to do this using some preprocessor library macro ?