Update only certain songs from tag source?

Anyone know of a way to only pull down certain songs from a tag source look up?

For example I have some albums with only tracks 3, 5, 6 and 9. When I look them up via the Amazon tag source it shows the entire track listing and if I say OK it turns 3, 5, 6, 9 into 1, 2, 3, 4 which isn't correct at all.

What I'd like is a way to either select the tracks I want it to map, or for it to guess based on the current track number or another column that shows what track the tag data will be applied to. I run into this quite a bit with single songs when I'm looking to update album art.

While on the topic I'd also like a way to select what tags will actually get updated from the tag source. Sometimes I just want the album art, not everything or I just want the art + year + album but I don't want it to touch artist or track.

Any thoughts or is this a feature request?