Different excerpt lengths for different categories

Hello,

I would like different categories to have different excerpt lengths. I have set in the functions a default one by doing

add_filter('excerpt_length', 'my_excerpt_length');
	function my_excerpt_length($length) {
		return 10;
	}

but unfortunately this is global. I would like category id 1 to be 10 and category 2 to be 100.

Is this possible?

Many thanks in advance.

Dave.