formula to lookup last entry in a list?

I have a list of account balances in one column. How can I pick up only the bottom number in that column? I have 20 worksheets and want a total across all worksheets of the last number listed in a particular column but each worksheet is different because they contain a different number of rows with activity. So, if in col. C I have:

$482
$1,000
$899
$456
$231

... then I want $231 to be what is captured for that worksheet, but if the 2nd worksheet contains:

$500
$1000
$344

... then I want $344 to be what is captured for worksheet 2. Does that make sense. In the end I want to sum $231, $344.... etc.

Thanks if you can help.