Volume pricing

[trendsinthreads]

I tried to set up a volume pricing promotion for discounts when you buy more than one item.  I thought Ebay recently posted that this could be applied across selected listings and not just apply if a buyer purchased multiples of the same item.  Since I sell women’s clothing, though I do have some listings with multiple quantities of the same item, the majority of my listings are only one item.  Is there a way for me to offer discounts on multiple items purchased as selected to be applied in the promotion (and not only to multiples purchased of the same item)? 
I thought you could set it up so that there would be a link to the other items in my store that were eligible for volume pricing discount (for example, someone could buy one dress along with a second dress from a different listing to get the discount).  
if anyone knows whether this can be accomplished, I would appreciate the info!