I think I was confused, because since I purchased MS Office 2007 and found
that this has discusting and unefficient GUI, I started to use OpenOffice.org
Calc much more, and Calcs undo works with deleted sheets too. Now, after a
while, I used Excel again and was disappointed, thet the function does not
function there. Because quite frequent use in Calk I was almost sure, that
previous MS Excels had undo function for deleted worksheets too. My mistake!
Just another reason for switching to Calc, as I have not seen any news or
even rumors, that Microsoft will fix that crappy interface!