I'm using LibreOffice, so I had to change your "]" character to "$" and it worked! Sort of.
I found that when I typed that formula into a cell, it worked, but if I renamed the sheet, the cell would not get the renamed value, the cell data was stale. I found that if I copied the formula into another cell, the new cell would show the properly value. Maybe it's an artifact of LibreOffice?
Is that the only way to get the sheet name? Your idea seems a bit round-about. Also, if Excel wants "]" in the search string, I can't use the same file for both Excel and LibreOffice users.
Thanks very much!