=LOOKUP(9.99999999999999E+307,INDIRECT("'"&A1&"'!H :H"))

Actually, some worksheets seem to freeze for a few seconds, I'm
guessing due to this long number. I tried to replace
9.99999999999999E+307 for 10000 (I was guessing that this long number
would be the number of rows in any one sheet and I never have more
than 1000). Worksheets never again froze for a few seconds, but I had
however one worksheet that returned an odd amount for an account's
balance (it wasn't the most current). I added another 0 to the 10000
and it worked again... :| So... 9.99999999999999E+307 is kind of a
long number that's causing delays, but I guess 10000 is not long
enough to achieve what I want in every possible case... What's
probably a good bet for a number that's the minimum required to return
the most current balance at the bottom of each sheet, considering that
every worksheet never goes beyond 1000 rows?

Thanks in advance!