Dear BrisbaneBob,
THis is a solution I reearched for your query...
http://www.mcgimpsey.com/excel/threedsumif.html
I have made a small list of all the Tab Names in the cOLUMN O from 06 till O9 which can also be automated but that you can do a ta later stage..
=SUMPRODUCT(SUMIF(INDIRECT("'"&$O$6:$O$9&"'!$A$6:$A$17"),A6,INDIRECT("'"&$O$6:$O$9&"'!$B$6:$B$17")))
This is just a single formula which gives the result for all the sheets....
Now you can work on getting the SHeet Names automatically in the Lists of Column O and also use an extended INDIRECT FUNCTION TO update the Range "'!$B$6:$B$17" so that you could drag the formula sideways..
SUBSTITUTE(ADDRESS(1,COLUMN(),1),"1","",1)&"6:"&SUBSTITUTE(ADDRESS(1,COLUMN(),1),"1","",1)&"17"
For getting the Range $B$6:$B$17
Hope this helps..
Warm REgards
e4excel
Bookmarks