Is there a way to create a "select all" option at top of dropdown list?

[doktorfroyd]

Thanks DrByte! I have in fact figured out how to make options/values pre-selected before they're added to the cart. I think I need to re-word my initial question though. I put "select all option from a dropdown list" but I think checkboxes are probably the only way to go for what I'm trying to do.

If I have a product called "monkeybuscuits", I want to have an option - let's call it "monkeybuscuitsDivX" - that has fifteen .rar file parts, which means fifteen checkboxes involved "part1.rar", "part2.rar, "part3.rar" and so on and so on. Why not just make them all required and therefore preselected so that all the customer has to do is click "add this to my cart"? Because there will also be another option "monkeybuscuits.iso" that's going to have twenty .rar file parts, therefore twenty checkboxes of it's own. If I make them all preselected, the customer's not going to be able to choose only one of the options unless he manually unchecks a whole bunch of boxes.

There must be a way to modify one of the Zen cart .php files on my server so that I can create a "select all" checkbox. Probably a very basic code for those who know how to write it, and I think I'm going to educate myself in .php, but I'm hoping someone could help me with this one specific request as I'd like to impliment it asap.

[DrByte]

As the system is architected right now, I think you'd still need to have all the 15 and 20 separate checkboxes (actually radio buttons are better, because they technically can't be deselected) for each "file".
But then you might be able to use some custom jQuery or other fancy javascript stuff to insert some buttons onto the page that invite the user to click to auto-select all the buttons for one file-format vs the other.
But that's all pretty much outside actual Zen Cart core code, and more just custom templating and javascripting. And actually fairly complex because all the attributes on each product are built dynamically and so the javascript will need to take all that into account in order to know what items to "check" etc. Not something you're gonna write overnight.