Brian Ballek wrote...
....
across multiple sheets where the data to be summed won't always
be in the same cell reference. But it should always have the same
label 2 cells to the left. Could this method be enhanced to have
the formula find the right data in all sheets within the
Start:End range based on a given text string?
....

No.

If you need possibly different cells on different worksheets, you
can't use 3D references. You could use indirect referencing, but you'd
need a list of the names of all the worksheets you need to process. If
you had such a list in a range named WSLST, and if the labels would
always be in col C and the corresponding values always in col E, and
the labels and values of interest always between rows 5 and 100, and
there were no duplicate labels in C5:C100 in any of these worksheets,
you could use

=SUMPRODUCT(SUMIF(INDIRECT("'"&WSLST&"'!C5:C100"), <label_sought,
INDIRECT("'"&WSLST&"'!E5:E100")))