Selecting Multiple Items?

I'd like to make an offer of multiple items on a marketplace trade, however the only way to do so seems to select a bunch of items at once. This doesn't work for me, however, because the items I'd like to select are on complete opposite ends of the little scroll and I am keeping the items in between them. When I try to select two at once it deselects the previous one. Anyone know how?

That happens to me too, I have no idea how.

Ctrl click. Hold down the control key to click multiple items that aren't in a row, i.e. one Carrot and one Yellow Apple, if you want a bunch of items in a row, i.e. 20 Driving Bridles, use Shift  and click.