Change rewrite rules for categories only

Is there a way to change the rewrite rules for the category ONLY using wp_rewrite?

i want category to be %category%.html and posts to be %category%-%postname%.html and i think the rule for the category is eating up also what’s supposed to be for the posts (Was using Advanced Permalinks and in its debug section category rule was (.+?).html which also matches one for posts)..

thnx in advance..