Here is a solution that will work depending on how many different cells you're talking about.
Define the cell (in any function) like this:
and call it like this:
irow = length(getappdata(0,LastPullTable));
The problem is (how I see it) that you have to be using some sort function to reference a string or else "length" will just give you the length of the string.
This solution will work, but it may not be efficient or reasonable depending on what kind of data you're dealing with and the amount present.