If your sheet names follow some kind of pattern/sequence like the default
sheet names: Sheet2, Sheet3, Sheet4...Sheet25:
=SUMPRODUCT(SUMIF(INDIRECT("'Sheet"&ROW(INDIRECT("2:25"))&"'!A1:A10"),A1,INDIRECT("'Sheet"&ROW(INDIRECT("2:25"))&"'!B1:B10")))
If your sheet names are unique like Alaska, Alabama, Arizona:
You have to list the sheet names in a range of cells, say, H1:H25, then:
=SUMPRODUCT(SUMIF(INDIRECT("'"&H$1:H$25&"'!A1:A10"),A1,INDIRECT("'"&H$1:H$25&"'!B1:B10")))
Both formulas do the same thing:
Sumif(Sheet_names!A1:A10,A1,Sheet_names!B1:B10) then Sumproduct adds them
all up.
Biff