Javascript From Imagemap

I have an image map, and want the user to be able to click on the map to select or deselect that area. ie assume the map is divided into 50 areas numbered 1 -50, I want a text input box on a form when someone clicks area 5 say, that choice will appear in the textbox, now they click 20,25 and 30 and the text box displays 5,20,25,30. Now if they click 25 again I need that choice to be removed thus the textbox becomes 5,20,30. I'm sure you get the picture.

Utimately I would like the areas to appear in a text area on different lines with a description beside, ie

<textarea>
5 - Red Area
20 - Blue Area
25 - Pink Area
30 - Orange Area
</textarea>

but a text box would be great for starters.