Cheeky question for extremely simple plugin

Hello,

Can I ask a cheeky question?

I simply want to replace the category box in the admin to this:

wp_dropdown_categories( “hierarchical=0&hide_empty=0&child_of=1” )

when the user is not an admin. As I only want users to post to the subcats of category id 1.

This is an extremely simple plugin isn’t it? Perhaps I could even do this in functions.php of my theme?

so something like:

if (!current_user_can(‘level_10’)){
wp_dropdown_categories( “hierarchical=0&hide_empty=0&child_of=1” );
}
}

But I think I need to create a function? Can some one point me in the right direction. Or if you write it, ill send $10 via paypal to you.

Cheers, Steven