Adam, I have found that the following works extremely well:
on your iWeb page, place a TEXT BOX with some text in it- a code word that you know appears nowhere in the page, such as VIEWCARTGOESHERE or something. Everywhere you want the View Cart button add this text box. Text box should be the size of the button. Do this for other e-junkie buttons you want, and just change the code name. you can use, forexample, ADDCARTBUTTON1 or whatever you like. Publish your pages to a folder.
Download a program called MassReplaceIt http://www.hexmonkeysoftware.com/
Launch MassReplaceIt and configure as follows:
MASK TAB>ADD Extension is .html and select radio button for "all criteria"
OPTIONS TAB>Check Serach:Contents, Location:Entire File/filename, Options Case Sensitive, Search whole words only
OPTIONS TAB>OPEN PREFERENCES>GENERAL>check add items to the front search, add the folder, search the folder's name and contents, ignore invisible files, apply mask when searching begins.
Then go to the Find TAB and enter your code word that you used (VIEWCARTGOESHERE). Then under Replace copy the html code that e-junkie provides you. Repeat this process for all buttons on your iweb pages.
Then under the FILES tab, add the files from your published folder. Then click Replace.
Mass ReplaceIt will search all the files you add for the code words and replace the code words with the html code. You can save the query for using later. I currently have one query with all my buttons programmed in to find and replace. Every time I publish my site I just run MassReplaceIt and it puts all the right html code in for me. Since it saves the query including which files it looks at, it's pretty automated. If you have questions, just ask. Hope this helps.