Problem in Imagemapping

Question

I have an image and a listbox
when i click the first item of the listbox and then click on the image, I need to print a red dot on whenever I click on the image. and also get the co ordinate of the point.

BUt now, I want to select second item on the listbox and then again click on the image, now I need to print a blue dot on the image where i click without removing the previous red dot and also get the co ordinate of the second click.

And this way, I have ten to twelve items in the listbox, and I want to get differenet coloured points on the image indicating where the user clicked.
How can I do  it
Pls help.