I have an apllication where I examine 5500 rows to see if empty and, if so,
"Hide" the row. Otherwise, "Unhide". After this macro has been run a few
times, the macro slows to a crawl.

My hypothesis is that Excel's internal "Undo" feature is tracking these
changes and I am filling up memory set aside for "Undo"s -- which, then
causes Excel to clear the oldest entry in the stack in order to add the
next. At which point it crawls.

I've seen this outside of VBA in Exel proper when I go to do a "Find and
Replace All" on a large data retrieval area. The replace zips along fine,
then slows, then crawls.

I'm wondering if my VBA "Unhide"/"Hide" code is running into something
similar. Hope I've described the symptoms well enough. Any ideas would be
welcome. Thanks.