Thank you for the response! Unfortunately, it looks like your suggestions might not work for me (unless I'm overlooking something).
I think I do need to generate a value list from my table (it has over 70,000 unique z-values), but I can't seem to use the script you linked to. My guess is that this because I'm using 9.3.1 rather than 10 (I can't use 10 because the field station I'm making this for is not planning to upgrade to 10 anytime soon).
I think I may have to accept the fact that a Python approach is necessary here. I just wish it wasn't so difficult to script lists of values for user inputs (in this case, Date and Time values from my table).