Why not try limiting the number of elements that MicroStrategy brings back in the element prompt? You can do this in the Web preferences or in the desktop thru the Project Configuration settings. Let's say you've got 10,000 elements, you can specify it to only bring back the first 1000, and speed up the retrieval process that way. Also, once you've got some of them back, you can then search for others.
In Desktop (I've got 7.2.2) look at the Project Configuration, Project Definition, Advanced tab, and see the "Attribute Elements Browsing" settings. Or in web, look at Preferences, General making sure you're on the Project Defaults preferences level, and check out the Incremental Fetch option. Play with those settings, and see if that will help speed up your element prompts, and allow you to do what you want to do. Don't forget to check out the searching capability as well, once you've retrieved the first X number of element rows for an attribute.
Hope that helps.
Nate